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fs: Add a missing permission check to do_umount 

Accessing do_remount_sb should require global CAP_SYS_ADMIN, but
only one of the two call sites was appropriately protected.

Fixes CVE-2014-7975.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
This commit is contained in:
Andy Lutomirski 2014-10-08 12:32:47 -07:00
parent bfe01a5ba2
commit a1480dcc3c
1 changed files with 2 additions and 0 deletions
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2
fs/namespace.c
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@ -1356,6 +1356,8 @@ static int do_umount(struct mount *mnt, int flags)
* Special case for "unmounting" root ...
* we just try to remount it readonly.
*/
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
down_write(&sb->s_umount);
if (!(sb->s_flags & MS_RDONLY))
retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);