Eric Paris <eparis@xxxxxxxxxx> writes: > On Fri, 2009-08-07 at 06:05 -0400, Amerigo Wang wrote: >> V2 -> V3: >> Call notify_change() before clearing suid/sgid. >> Thanks to OGAWA Hirofumi. >> >> V1 -> V2: >> Introduce dentry_remove_suid(), and use it in do_truncate(). >> Thanks to Eric Paris. >> >> >> When suid is set and the non-owner user has write permission, >> any writing into this file should be allowed and suid should be >> removed after that. >> >> However, current kernel only allows writing without truncations, >> when we do truncations on that file, we get EPERM. This is a bug. >> >> Steps to reproduce this bug: >> >> % ls -l rootdir/file1 >> -rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1 >> % echo h > rootdir/file1 >> zsh: operation not permitted: rootdir/file1 >> % ls -l rootdir/file1 >> -rwsrwsrwx 1 root root 3 Jun 25 15:42 rootdir/file1 >> % echo h >> rootdir/file1 >> % ls -l rootdir/file1 >> -rwxrwxrwx 1 root root 5 Jun 25 16:34 rootdir/file1 >> >> This patch fixes it. >> >> Signed-off-by: WANG Cong <amwang@xxxxxxxxxx> >> Cc: Eric Sandeen <esandeen@xxxxxxxxxx> >> Cc: Eric Paris <eparis@xxxxxxxxxx> >> Cc: Eugene Teo <eteo@xxxxxxxxxx> >> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> >> Cc: hirofumi@xxxxxxxxxxxxxxxxxx > > I was thinking about this and kept telling myself I was going to test v2 > before I ack/nak. Clearly we shouldn't for the dropping of SUID if the > process didn't have permission to change the ATTR_SIZE. > > Acked-by: Eric Paris <eparis@xxxxxxxxxx> BTW, Do you know why doesn't security modules fix the handling of do_truncate() (i.e. ATTR_MODE | ATTR_SIZE). And why doesn't it allow to pass ATTR_FORCE for it? Thanks. -- OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
