Messages in this thread Patch in this message | | | Date | Wed, 04 Jun 2008 00:25:14 +0200 | Subject | [parch 3/4] vfs: utimensat(): fix error checking for {UTIME_NOW,UTIME_OMIT} case | From | Michael Kerrisk <> |
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The POSIX.1 draft spec for utimensat() says that to do anything other than setting both timestamps to a time other than the current time (i.e., times is not NULL, and both tv_nsec fields are not UTIME_NOW and both tv_nsec fields are not UTIME_OMIT), either:
a) the caller's effective user ID must match the file owner; or b) the caller must have appropriate privileges.
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.
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 simpler, and can be more easily read as being correct.
CC: 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>
--- linux-2.6.26-rc4/fs/utimes.c 2008-06-03 23:11:53.000000000 +0200 +++ linux-2.6.26-rc4-utimensat-fix-v4/fs/utimes.c 2008-06-03 23:04:48.000000000 +0200 @@ -40,14 +40,9 @@
#endif
-static bool nsec_special(long nsec) -{ - return nsec == UTIME_OMIT || nsec == UTIME_NOW; -} - static bool nsec_valid(long nsec) { - if (nsec_special(nsec)) + if (nsec == UTIME_OMIT || nsec == UTIME_NOW) return true;
return nsec >= 0 && nsec <= 999999999; @@ -135,8 +130,7 @@ * UTIME_NOW, then need to check permissions, because * inode_change_ok() won't do it. */ - if (!times || (nsec_special(times[0].tv_nsec) && - nsec_special(times[1].tv_nsec))) { + if (!times) { error = -EACCES; if (IS_IMMUTABLE(inode)) goto mnt_drop_write_and_out; @@ -151,6 +145,18 @@ goto mnt_drop_write_and_out; } } + } else if ((times[0].tv_nsec == UTIME_NOW && + times[1].tv_nsec == UTIME_OMIT) + || + (times[0].tv_nsec == UTIME_OMIT && + times[1].tv_nsec == UTIME_NOW)) { + error =-EPERM; + + if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) + goto mnt_drop_write_and_out; + + if (!is_owner_or_cap(inode)) + goto mnt_drop_write_and_out; } mutex_lock(&inode->i_mutex); error = notify_change(dentry, &newattrs);
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