Attachment 311724 Details for Bug 455275 – Proposed upstream patch

[patch] Proposed upstream patch

vfs-fix-permission-checking-in-sys_utimensat.patch (text/plain), 2.31 KB, created by Eugene Teo (Security Response) on 2008-07-14 16:27:15 UTC

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Creator: Eugene Teo (Security Response)

Created: 2008-07-14 16:27:15 UTC

Size: 2.31 KB

patch

obsolete

>From 02c6be615f1fcd37ac5ed93a3ad6692ad8991cd9 Mon Sep 17 00:00:00 2001
>From: Miklos Szeredi <mszeredi@suse.cz>
>Date: Thu, 1 May 2008 04:34:45 -0700
>Subject: [PATCH] vfs: fix permission checking in sys_utimensat
>
>If utimensat() is called with both times set to UTIME_NOW or one of them to
>UTIME_NOW and the other to UTIME_OMIT, then it will update the file time
>without any permission checking.
>
>I don't think this can be used for anything other than a local DoS, but could
>be quite bewildering at that (e.g.  "Why was that large source tree rebuilt
>when I didn't modify anything???")
>
>This affects all kernels from 2.6.22, when the utimensat() syscall was
>introduced.
>
>Fix by doing the same permission checking as for the "times == NULL" case.
>
>Thanks to Michael Kerrisk, whose utimensat-non-conformances-and-fixes.patch in
>-mm also fixes this (and breaks other stuff), only he didn't realize the
>security implications of this bug.
>
>Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
>Cc: Ulrich Drepper <drepper@redhat.com>
>Cc: Michael Kerrisk <mtk-manpages@gmx.net>
>Cc: <stable@kernel.org>
>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>---
> fs/utimes.c |   17 +++++++++++++++--
> 1 files changed, 15 insertions(+), 2 deletions(-)
>
>diff --git a/fs/utimes.c b/fs/utimes.c
>index a2bef77..af059d5 100644
>--- a/fs/utimes.c
>+++ b/fs/utimes.c
>@@ -40,9 +40,14 @@ asmlinkage long sys_utime(char __user *filename, struct utimbuf __user *times)
> 
> #endif
> 
>+static bool nsec_special(long nsec)
>+{
>+	return nsec == UTIME_OMIT || nsec == UTIME_NOW;
>+}
>+
> static bool nsec_valid(long nsec)
> {
>-	if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
>+	if (nsec_special(nsec))
> 		return true;
> 
> 	return nsec >= 0 && nsec <= 999999999;
>@@ -119,7 +124,15 @@ long do_utimes(int dfd, char __user *filename, struct timespec *times, int flags
> 			newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
> 			newattrs.ia_valid |= ATTR_MTIME_SET;
> 		}
>-	} else {
>+	}
>+
>+	/*
>+	 * If times is NULL or both times are either UTIME_OMIT or
>+	 * 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))) {
> 		error = -EACCES;
>                 if (IS_IMMUTABLE(inode))
> 			goto mnt_drop_write_and_out;
>-- 
>1.5.5.1
>

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Attachments on bug 455275: 311724