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UBSAN uses compile-time instrumentation to catch undefined behavior (UB). Compiler inserts code that perform certain kinds of checks before operations that could cause UB. If check fails (i.e. UB detected) __ubsan_handle_* function called to print error message. So the most of the work is done by compiler. This patch just implements ubsan handlers printing errors. GCC has this capability since 4.9.x [1] (see -fsanitize=undefined option and its suboptions). However GCC 5.x has more checkers implemented [2]. Article [3] has a bit more details about UBSAN in the GCC. [1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html [2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html [3] - http://developerblog.redhat.com/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/ Issues which UBSAN has found thus far are: Found bugs: * out-of-bounds access -97840cb67f("netfilter: nfnetlink: fix insufficient validation in nfnetlink_bind") undefined shifts: *d48458d4a7("jbd2: use a better hash function for the revoke table") *10632008b9("clockevents: Prevent shift out of bounds") * 'x << -1' shift in ext4 - http://lkml.kernel.org/r/<5444EF21.8020501@samsung.com> * undefined rol32(0) - http://lkml.kernel.org/r/<1449198241-20654-1-git-send-email-sasha.levin@oracle.com> * undefined dirty_ratelimit calculation - http://lkml.kernel.org/r/<566594E2.3050306@odin.com> * undefined roundown_pow_of_two(0) - http://lkml.kernel.org/r/<1449156616-11474-1-git-send-email-sasha.levin@oracle.com> * [WONTFIX] undefined shift in __bpf_prog_run - http://lkml.kernel.org/r/<CACT4Y+ZxoR3UjLgcNdUm4fECLMx2VdtfrENMtRRCdgHB2n0bJA@mail.gmail.com> WONTFIX here because it should be fixed in bpf program, not in kernel. signed overflows: *32a8df4e0b("sched: Fix odd values in effective_load() calculations") * mul overflow in ntp - http://lkml.kernel.org/r/<1449175608-1146-1-git-send-email-sasha.levin@oracle.com> * incorrect conversion into rtc_time in rtc_time64_to_tm() - http://lkml.kernel.org/r/<1449187944-11730-1-git-send-email-sasha.levin@oracle.com> * unvalidated timespec in io_getevents() - http://lkml.kernel.org/r/<CACT4Y+bBxVYLQ6LtOKrKtnLthqLHcw-BMp3aqP3mjdAvr9FULQ@mail.gmail.com> * [NOTABUG] signed overflow in ktime_add_safe() - http://lkml.kernel.org/r/<CACT4Y+aJ4muRnWxsUe1CMnA6P8nooO33kwG-c8YZg=0Xc8rJqw@mail.gmail.com> [akpm@linux-foundation.org: fix unused local warning] [akpm@linux-foundation.org: fix __int128 build woes] Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michal Marek <mmarek@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Yury Gribov <y.gribov@samsung.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Kostya Serebryany <kcc@google.com> Cc: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
84 lines
3.1 KiB
Text
84 lines
3.1 KiB
Text
Undefined Behavior Sanitizer - UBSAN
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Overview
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--------
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UBSAN is a runtime undefined behaviour checker.
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UBSAN uses compile-time instrumentation to catch undefined behavior (UB).
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Compiler inserts code that perform certain kinds of checks before operations
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that may cause UB. If check fails (i.e. UB detected) __ubsan_handle_*
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function called to print error message.
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GCC has that feature since 4.9.x [1] (see -fsanitize=undefined option and
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its suboptions). GCC 5.x has more checkers implemented [2].
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Report example
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---------------
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================================================================================
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UBSAN: Undefined behaviour in ../include/linux/bitops.h:110:33
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shift exponent 32 is to large for 32-bit type 'unsigned int'
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CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.0-rc1+ #26
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0000000000000000 ffffffff82403cc8 ffffffff815e6cd6 0000000000000001
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ffffffff82403cf8 ffffffff82403ce0 ffffffff8163a5ed 0000000000000020
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ffffffff82403d78 ffffffff8163ac2b ffffffff815f0001 0000000000000002
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Call Trace:
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[<ffffffff815e6cd6>] dump_stack+0x45/0x5f
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[<ffffffff8163a5ed>] ubsan_epilogue+0xd/0x40
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[<ffffffff8163ac2b>] __ubsan_handle_shift_out_of_bounds+0xeb/0x130
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[<ffffffff815f0001>] ? radix_tree_gang_lookup_slot+0x51/0x150
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[<ffffffff8173c586>] _mix_pool_bytes+0x1e6/0x480
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[<ffffffff83105653>] ? dmi_walk_early+0x48/0x5c
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[<ffffffff8173c881>] add_device_randomness+0x61/0x130
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[<ffffffff83105b35>] ? dmi_save_one_device+0xaa/0xaa
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[<ffffffff83105653>] dmi_walk_early+0x48/0x5c
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[<ffffffff831066ae>] dmi_scan_machine+0x278/0x4b4
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[<ffffffff8111d58a>] ? vprintk_default+0x1a/0x20
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[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
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[<ffffffff830b2240>] setup_arch+0x405/0xc2c
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[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
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[<ffffffff830ae053>] start_kernel+0x83/0x49a
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[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
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[<ffffffff830ad386>] x86_64_start_reservations+0x2a/0x2c
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[<ffffffff830ad4f3>] x86_64_start_kernel+0x16b/0x17a
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================================================================================
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Usage
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-----
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To enable UBSAN configure kernel with:
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CONFIG_UBSAN=y
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and to check the entire kernel:
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CONFIG_UBSAN_SANITIZE_ALL=y
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To enable instrumentation for specific files or directories, add a line
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similar to the following to the respective kernel Makefile:
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For a single file (e.g. main.o):
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UBSAN_SANITIZE_main.o := y
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For all files in one directory:
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UBSAN_SANITIZE := y
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To exclude files from being instrumented even if
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CONFIG_UBSAN_SANITIZE_ALL=y, use:
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UBSAN_SANITIZE_main.o := n
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and:
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UBSAN_SANITIZE := n
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Detection of unaligned accesses controlled through the separate option -
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CONFIG_UBSAN_ALIGNMENT. It's off by default on architectures that support
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unaligned accesses (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). One could
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still enable it in config, just note that it will produce a lot of UBSAN
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reports.
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References
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----------
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[1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
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[2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
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