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![Greg Kroah-Hartman](/assets/img/avatar_default.png)
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
352 lines
10 KiB
C
352 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Variant of atomic_t specialized for reference counts.
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*
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* The interface matches the atomic_t interface (to aid in porting) but only
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* provides the few functions one should use for reference counting.
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*
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* It differs in that the counter saturates at UINT_MAX and will not move once
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* there. This avoids wrapping the counter and causing 'spurious'
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* use-after-free issues.
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*
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* Memory ordering rules are slightly relaxed wrt regular atomic_t functions
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* and provide only what is strictly required for refcounts.
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*
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* The increments are fully relaxed; these will not provide ordering. The
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* rationale is that whatever is used to obtain the object we're increasing the
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* reference count on will provide the ordering. For locked data structures,
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* its the lock acquire, for RCU/lockless data structures its the dependent
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* load.
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*
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* Do note that inc_not_zero() provides a control dependency which will order
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* future stores against the inc, this ensures we'll never modify the object
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* if we did not in fact acquire a reference.
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*
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* The decrements will provide release order, such that all the prior loads and
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* stores will be issued before, it also provides a control dependency, which
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* will order us against the subsequent free().
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*
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* The control dependency is against the load of the cmpxchg (ll/sc) that
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* succeeded. This means the stores aren't fully ordered, but this is fine
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* because the 1->0 transition indicates no concurrency.
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*
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* Note that the allocator is responsible for ordering things between free()
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* and alloc().
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*
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*/
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#include <linux/refcount.h>
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#include <linux/bug.h>
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#ifdef CONFIG_REFCOUNT_FULL
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/**
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* refcount_add_not_zero - add a value to a refcount unless it is 0
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* @i: the value to add to the refcount
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* @r: the refcount
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*
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* Will saturate at UINT_MAX and WARN.
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*
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* Provides no memory ordering, it is assumed the caller has guaranteed the
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* object memory to be stable (RCU, etc.). It does provide a control dependency
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* and thereby orders future stores. See the comment on top.
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*
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* Use of this function is not recommended for the normal reference counting
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* use case in which references are taken and released one at a time. In these
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* cases, refcount_inc(), or one of its variants, should instead be used to
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* increment a reference count.
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*
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* Return: false if the passed refcount is 0, true otherwise
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*/
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bool refcount_add_not_zero(unsigned int i, refcount_t *r)
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{
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unsigned int new, val = atomic_read(&r->refs);
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do {
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if (!val)
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return false;
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if (unlikely(val == UINT_MAX))
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return true;
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new = val + i;
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if (new < val)
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new = UINT_MAX;
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} while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
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WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
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return true;
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}
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EXPORT_SYMBOL(refcount_add_not_zero);
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/**
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* refcount_add - add a value to a refcount
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* @i: the value to add to the refcount
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* @r: the refcount
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*
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* Similar to atomic_add(), but will saturate at UINT_MAX and WARN.
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*
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* Provides no memory ordering, it is assumed the caller has guaranteed the
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* object memory to be stable (RCU, etc.). It does provide a control dependency
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* and thereby orders future stores. See the comment on top.
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*
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* Use of this function is not recommended for the normal reference counting
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* use case in which references are taken and released one at a time. In these
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* cases, refcount_inc(), or one of its variants, should instead be used to
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* increment a reference count.
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*/
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void refcount_add(unsigned int i, refcount_t *r)
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{
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WARN_ONCE(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
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}
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EXPORT_SYMBOL(refcount_add);
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/**
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* refcount_inc_not_zero - increment a refcount unless it is 0
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* @r: the refcount to increment
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*
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* Similar to atomic_inc_not_zero(), but will saturate at UINT_MAX and WARN.
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*
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* Provides no memory ordering, it is assumed the caller has guaranteed the
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* object memory to be stable (RCU, etc.). It does provide a control dependency
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* and thereby orders future stores. See the comment on top.
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*
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* Return: true if the increment was successful, false otherwise
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*/
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bool refcount_inc_not_zero(refcount_t *r)
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{
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unsigned int new, val = atomic_read(&r->refs);
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do {
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new = val + 1;
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if (!val)
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return false;
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if (unlikely(!new))
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return true;
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} while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
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WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
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return true;
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}
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EXPORT_SYMBOL(refcount_inc_not_zero);
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/**
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* refcount_inc - increment a refcount
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* @r: the refcount to increment
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*
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* Similar to atomic_inc(), but will saturate at UINT_MAX and WARN.
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*
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* Provides no memory ordering, it is assumed the caller already has a
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* reference on the object.
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*
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* Will WARN if the refcount is 0, as this represents a possible use-after-free
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* condition.
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*/
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void refcount_inc(refcount_t *r)
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{
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WARN_ONCE(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n");
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}
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EXPORT_SYMBOL(refcount_inc);
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/**
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* refcount_sub_and_test - subtract from a refcount and test if it is 0
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* @i: amount to subtract from the refcount
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* @r: the refcount
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*
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* Similar to atomic_dec_and_test(), but it will WARN, return false and
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* ultimately leak on underflow and will fail to decrement when saturated
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* at UINT_MAX.
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*
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* Provides release memory ordering, such that prior loads and stores are done
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* before, and provides a control dependency such that free() must come after.
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* See the comment on top.
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*
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* Use of this function is not recommended for the normal reference counting
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* use case in which references are taken and released one at a time. In these
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* cases, refcount_dec(), or one of its variants, should instead be used to
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* decrement a reference count.
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*
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* Return: true if the resulting refcount is 0, false otherwise
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*/
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bool refcount_sub_and_test(unsigned int i, refcount_t *r)
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{
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unsigned int new, val = atomic_read(&r->refs);
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do {
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if (unlikely(val == UINT_MAX))
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return false;
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new = val - i;
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if (new > val) {
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WARN_ONCE(new > val, "refcount_t: underflow; use-after-free.\n");
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return false;
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}
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} while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
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return !new;
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}
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EXPORT_SYMBOL(refcount_sub_and_test);
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/**
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* refcount_dec_and_test - decrement a refcount and test if it is 0
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* @r: the refcount
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*
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* Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
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* decrement when saturated at UINT_MAX.
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*
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* Provides release memory ordering, such that prior loads and stores are done
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* before, and provides a control dependency such that free() must come after.
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* See the comment on top.
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*
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* Return: true if the resulting refcount is 0, false otherwise
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*/
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bool refcount_dec_and_test(refcount_t *r)
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{
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return refcount_sub_and_test(1, r);
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}
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EXPORT_SYMBOL(refcount_dec_and_test);
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/**
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* refcount_dec - decrement a refcount
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* @r: the refcount
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*
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* Similar to atomic_dec(), it will WARN on underflow and fail to decrement
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* when saturated at UINT_MAX.
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*
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* Provides release memory ordering, such that prior loads and stores are done
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* before.
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*/
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void refcount_dec(refcount_t *r)
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{
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WARN_ONCE(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
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}
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EXPORT_SYMBOL(refcount_dec);
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#endif /* CONFIG_REFCOUNT_FULL */
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/**
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* refcount_dec_if_one - decrement a refcount if it is 1
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* @r: the refcount
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*
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* No atomic_t counterpart, it attempts a 1 -> 0 transition and returns the
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* success thereof.
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*
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* Like all decrement operations, it provides release memory order and provides
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* a control dependency.
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*
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* It can be used like a try-delete operator; this explicit case is provided
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* and not cmpxchg in generic, because that would allow implementing unsafe
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* operations.
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*
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* Return: true if the resulting refcount is 0, false otherwise
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*/
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bool refcount_dec_if_one(refcount_t *r)
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{
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int val = 1;
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return atomic_try_cmpxchg_release(&r->refs, &val, 0);
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}
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EXPORT_SYMBOL(refcount_dec_if_one);
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/**
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* refcount_dec_not_one - decrement a refcount if it is not 1
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* @r: the refcount
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*
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* No atomic_t counterpart, it decrements unless the value is 1, in which case
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* it will return false.
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*
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* Was often done like: atomic_add_unless(&var, -1, 1)
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*
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* Return: true if the decrement operation was successful, false otherwise
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*/
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bool refcount_dec_not_one(refcount_t *r)
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{
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unsigned int new, val = atomic_read(&r->refs);
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do {
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if (unlikely(val == UINT_MAX))
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return true;
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if (val == 1)
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return false;
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new = val - 1;
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if (new > val) {
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WARN_ONCE(new > val, "refcount_t: underflow; use-after-free.\n");
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return true;
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}
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} while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
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return true;
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}
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EXPORT_SYMBOL(refcount_dec_not_one);
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/**
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* refcount_dec_and_mutex_lock - return holding mutex if able to decrement
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* refcount to 0
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* @r: the refcount
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* @lock: the mutex to be locked
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*
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* Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
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* to decrement when saturated at UINT_MAX.
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*
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* Provides release memory ordering, such that prior loads and stores are done
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* before, and provides a control dependency such that free() must come after.
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* See the comment on top.
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*
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* Return: true and hold mutex if able to decrement refcount to 0, false
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* otherwise
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*/
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bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
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{
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if (refcount_dec_not_one(r))
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return false;
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mutex_lock(lock);
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if (!refcount_dec_and_test(r)) {
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mutex_unlock(lock);
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return false;
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}
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return true;
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}
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EXPORT_SYMBOL(refcount_dec_and_mutex_lock);
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/**
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* refcount_dec_and_lock - return holding spinlock if able to decrement
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* refcount to 0
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* @r: the refcount
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* @lock: the spinlock to be locked
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*
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* Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
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* decrement when saturated at UINT_MAX.
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*
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* Provides release memory ordering, such that prior loads and stores are done
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* before, and provides a control dependency such that free() must come after.
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* See the comment on top.
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*
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* Return: true and hold spinlock if able to decrement refcount to 0, false
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* otherwise
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*/
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bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
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{
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if (refcount_dec_not_one(r))
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return false;
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spin_lock(lock);
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if (!refcount_dec_and_test(r)) {
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spin_unlock(lock);
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return false;
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}
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return true;
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}
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EXPORT_SYMBOL(refcount_dec_and_lock);
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