mirror of https://gitee.com/openkylin/linux.git
[patch for 2.6.26 3/4] vfs: utimensat(): fix error checking for {UTIME_NOW,UTIME_OMIT} case
The POSIX.1 draft spec for utimensat() says: Only a process with the effective user ID equal to the user ID of the file or with appropriate privileges may use futimens() or utimensat() with a non-null times argument that does not have both tv_nsec fields set to UTIME_NOW and does not have both tv_nsec fields set to UTIME_OMIT. If this condition is violated, then the error EPERM should result. However, the current implementation does not generate EPERM if one tv_nsec field is UTIME_NOW while the other is UTIME_OMIT. It should give this error for that case. This patch: a) Repairs that problem. b) Removes the now unneeded nsec_special() helper function. c) Adds some comments to explain the checks that are being performed. Thanks to Miklos, who provided comments on the previous iteration of this patch. As a result, this version is a little simpler and and its logic is better structured. Miklos suggested an alternative idea, migrating the is_owner_or_cap() checks into fs/attr.c:inode_change_ok() via the use of an ATTR_OWNER_CHECK flag. Maybe we could do that later, but for now I've gone with this version, which is IMO simpler, and can be more easily read as being correct. Acked-by: Miklos Szeredi <miklos@szeredi.hu> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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36
fs/utimes.c
36
fs/utimes.c
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@ -40,14 +40,9 @@ asmlinkage long sys_utime(char __user *filename, struct utimbuf __user *times)
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#endif
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static bool nsec_special(long nsec)
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{
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return nsec == UTIME_OMIT || nsec == UTIME_NOW;
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}
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static bool nsec_valid(long nsec)
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{
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if (nsec_special(nsec))
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if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
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return true;
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return nsec >= 0 && nsec <= 999999999;
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@ -106,7 +101,7 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
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times[1].tv_nsec == UTIME_NOW)
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times = NULL;
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/* Don't worry, the checks are done in inode_change_ok() */
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/* In most cases, the checks are done in inode_change_ok() */
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newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
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if (times) {
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error = -EPERM;
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@ -128,15 +123,26 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
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newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
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newattrs.ia_valid |= ATTR_MTIME_SET;
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}
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}
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/*
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* If times is NULL or both times are either UTIME_OMIT or
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* UTIME_NOW, then need to check permissions, because
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* inode_change_ok() won't do it.
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*/
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if (!times || (nsec_special(times[0].tv_nsec) &&
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nsec_special(times[1].tv_nsec))) {
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/*
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* For the UTIME_OMIT/UTIME_NOW and UTIME_NOW/UTIME_OMIT
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* cases, we need to make an extra check that is not done by
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* inode_change_ok().
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*/
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if (((times[0].tv_nsec == UTIME_NOW &&
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times[1].tv_nsec == UTIME_OMIT)
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(times[0].tv_nsec == UTIME_OMIT &&
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times[1].tv_nsec == UTIME_NOW))
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&& !is_owner_or_cap(inode))
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goto mnt_drop_write_and_out;
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} else {
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/*
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* If times is NULL (or both times are UTIME_NOW),
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* then we need to check permissions, because
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* inode_change_ok() won't do it.
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*/
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error = -EACCES;
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if (IS_IMMUTABLE(inode))
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goto mnt_drop_write_and_out;
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