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![Hin-Tak Leung](/assets/img/avatar_default.png)
HFSPLUS_ATTR_MAX_STRLEN (=127) is the limit of attribute names for the number of unicode character (UTF-16BE) storable in the HFS+ file system. Almost all the current usage of it is wrong, in relation to NLS to on-disk conversion. Except for one use calling hfsplus_asc2uni (which should stay the same) and its uses in calling hfsplus_uni2asc (which was corrected in the earlier patch in this series concerning usage of hfsplus_uni2asc), all the other uses are of the forms: - char buffer[size] - bound check: "if (namespace_adjusted_input_length > size) return failure;" Conversion between on-disk unicode representation and NLS char strings (in whichever direction) always needs to accommodate the worst-case NLS conversion, so all char buffers of that size need to have a NLS_MAX_CHARSET_SIZE x . The bound checks are all wrong, since they compare nls_length derived from strlen() to a unicode length limit. It turns out that all the bound-checks do is to protect hfsplus_asc2uni(), which can fail if the input is too large. There is only one usage of it as far as attributes are concerned, in hfsplus_attr_build_key(). It is in turn used by hfsplus_find_attr(), hfsplus_create_attr(), hfsplus_delete_attr(). Thus making sure that errors from hfsplus_asc2uni() is caught in hfsplus_attr_build_key() and propagated is sufficient to replace all the bound checks. Unpropagated errors from hfsplus_asc2uni() in the file catalog code was addressed recently in an independent patch "hfsplus: fix longname handling" by Sougata Santra. Before this patch, trying to set a 55 CJK character (in a UTF-8 locale, > 127/3=42) attribute plus user prefix fails with: $ setfattr -n user.`cat testing-string` -v `cat testing-string` \ testing-string setfattr: testing-string: Operation not supported and retrieving a stored long attributes is particular ugly(!): find /mnt/* -type f -exec getfattr -d {} \; getfattr: /mnt/testing-string: Input/output error with console log: [268008.389781] hfsplus: unicode conversion failed After the patch, both of the above works. FYI, the test attribute string is prepared with: echo -e -n \ "\xe9\x80\x99\xe6\x98\xaf\xe4\xb8\x80\xe5\x80\x8b\xe9\x9d\x9e\xe5" \ "\xb8\xb8\xe6\xbc\xab\xe9\x95\xb7\xe8\x80\x8c\xe6\xa5\xb5\xe5\x85" \ "\xb6\xe4\xb9\x8f\xe5\x91\xb3\xe5\x92\x8c\xe7\x9b\xb8\xe7\x95\xb6" \ "\xe7\x84\xa1\xe8\xb6\xa3\xe3\x80\x81\xe4\xbb\xa5\xe5\x8f\x8a\xe7" \ "\x84\xa1\xe7\x94\xa8\xe7\x9a\x84\xe3\x80\x81\xe5\x86\x8d\xe5\x8a" \ "\xa0\xe4\xb8\x8a\xe6\xaf\xab\xe7\x84\xa1\xe6\x84\x8f\xe7\xbe\xa9" \ "\xe7\x9a\x84\xe6\x93\xb4\xe5\xb1\x95\xe5\xb1\xac\xe6\x80\xa7\xef" \ "\xbc\x8c\xe8\x80\x8c\xe5\x85\xb6\xe5\x94\xaf\xe4\xb8\x80\xe5\x89" \ "\xb5\xe5\xbb\xba\xe7\x9b\xae\xe7\x9a\x84\xe5\x83\x85\xe6\x98\xaf" \ "\xe7\x82\xba\xe4\xba\x86\xe6\xb8\xac\xe8\xa9\xa6\xe4\xbd\x9c\xe7" \ "\x94\xa8\xe3\x80\x82" | tr -d ' ' (= "pointlessly long attribute for testing", elaborate Chinese in UTF-8 enoding). However, it is not possible to set double the size (110 + 5 is still under 127) in a UTF-8 locale: $setfattr -n user.`cat testing-string testing-string` -v \ `cat testing-string testing-string` testing-string setfattr: testing-string: Numerical result out of range 110 CJK char in UTF-8 is 330 bytes - the generic get/set attribute system call code in linux/fs/xattr.c imposes a 255 byte limit. One can use a combination of iconv to encode content, changing terminal locale for viewing, and an nls=cp932/cp936/cp949/cp950 mount option to fully use 127-unicode attribute in a double-byte locale. Also, as an additional information, it is possible to (mis-)use unicode half-width/full-width forms (U+FFxx) to write attributes which looks like english but not actually ascii. Thanks Anton Altaparmakov for reviewing the earlier ideas behind this change. [akpm@linux-foundation.org: fix build] [akpm@linux-foundation.org: fix build] Signed-off-by: Hin-Tak Leung <htl10@users.sourceforge.net> Cc: Anton Altaparmakov <anton@tuxera.com> Cc: Vyacheslav Dubeyko <slava@dubeyko.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Sougata Santra <sougata@tuxera.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
71 lines
1.7 KiB
C
71 lines
1.7 KiB
C
/*
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* linux/fs/hfsplus/xattr_trusted.c
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*
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* Vyacheslav Dubeyko <slava@dubeyko.com>
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*
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* Handler for trusted extended attributes.
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*/
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#include <linux/nls.h>
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#include "hfsplus_fs.h"
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#include "xattr.h"
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static int hfsplus_trusted_getxattr(struct dentry *dentry, const char *name,
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void *buffer, size_t size, int type)
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{
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char *xattr_name;
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int res;
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if (!strcmp(name, ""))
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return -EINVAL;
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xattr_name = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_ATTR_MAX_STRLEN + 1,
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GFP_KERNEL);
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if (!xattr_name)
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return -ENOMEM;
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strcpy(xattr_name, XATTR_TRUSTED_PREFIX);
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strcpy(xattr_name + XATTR_TRUSTED_PREFIX_LEN, name);
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res = hfsplus_getxattr(dentry, xattr_name, buffer, size);
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kfree(xattr_name);
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return res;
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}
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static int hfsplus_trusted_setxattr(struct dentry *dentry, const char *name,
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const void *buffer, size_t size, int flags, int type)
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{
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char *xattr_name;
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int res;
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if (!strcmp(name, ""))
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return -EINVAL;
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xattr_name = kmalloc(NLS_MAX_CHARSET_SIZE * HFSPLUS_ATTR_MAX_STRLEN + 1,
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GFP_KERNEL);
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if (!xattr_name)
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return -ENOMEM;
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strcpy(xattr_name, XATTR_TRUSTED_PREFIX);
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strcpy(xattr_name + XATTR_TRUSTED_PREFIX_LEN, name);
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res = hfsplus_setxattr(dentry, xattr_name, buffer, size, flags);
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kfree(xattr_name);
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return res;
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}
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static size_t hfsplus_trusted_listxattr(struct dentry *dentry, char *list,
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size_t list_size, const char *name, size_t name_len, int type)
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{
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/*
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* This method is not used.
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* It is used hfsplus_listxattr() instead of generic_listxattr().
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*/
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return -EOPNOTSUPP;
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}
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const struct xattr_handler hfsplus_xattr_trusted_handler = {
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.prefix = XATTR_TRUSTED_PREFIX,
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.list = hfsplus_trusted_listxattr,
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.get = hfsplus_trusted_getxattr,
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.set = hfsplus_trusted_setxattr,
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};
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