Messages in this thread Patch in this message | | | Date | Thu, 01 Jul 2010 10:35:19 -0700 | From | Greg KH <> | Subject | [patch 133/164] vfs: add NOFOLLOW flag to umount(2) |
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2.6.33-stable review patch. If anyone has any objections, please let me know.
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From: Miklos Szeredi <mszeredi@suse.cz>
commit db1f05bb85d7966b9176e293f3ceead1cb8b5d79 upstream.
Add a new UMOUNT_NOFOLLOW flag to umount(2). This is needed to prevent symlink attacks in unprivileged unmounts (fuse, samba, ncpfs).
Additionally, return -EINVAL if an unknown flag is used (and specify an explicitly unused flag: UMOUNT_UNUSED). This makes it possible for the caller to determine if a flag is supported or not.
CC: Eugene Teo <eugene@redhat.com> CC: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/namespace.c | 9 ++++++++- include/linux/fs.h | 2 ++ 2 files changed, 10 insertions(+), 1 deletion(-)
--- a/fs/namespace.c +++ b/fs/namespace.c @@ -1121,8 +1121,15 @@ SYSCALL_DEFINE2(umount, char __user *, n { struct path path; int retval; + int lookup_flags = 0; - retval = user_path(name, &path); + if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) + return -EINVAL; + + if (!(flags & UMOUNT_NOFOLLOW)) + lookup_flags |= LOOKUP_FOLLOW; + + retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); if (retval) goto out; retval = -EINVAL; --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1308,6 +1308,8 @@ extern int send_sigurg(struct fown_struc #define MNT_FORCE 0x00000001 /* Attempt to forcibily umount */ #define MNT_DETACH 0x00000002 /* Just detach from the tree */ #define MNT_EXPIRE 0x00000004 /* Mark for expiry */ +#define UMOUNT_NOFOLLOW 0x00000008 /* Don't follow symlink on umount */ +#define UMOUNT_UNUSED 0x80000000 /* Flag guaranteed to be unused */ extern struct list_head super_blocks; extern spinlock_t sb_lock;
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