This is a note to let you know that I've just added the patch titled

devpts: fix error handling in devpts_mntget()

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: devpts-fix-error-handling-in-devpts_mntget.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From c9cc8d01fb04117928830449388512a5047569c9 Mon Sep 17 00:00:00 2001

From: Eric Biggers ebiggers@google.com Date: Wed, 31 Jan 2018 00:49:18 -0800 Subject: devpts: fix error handling in devpts_mntget()

From: Eric Biggers ebiggers@google.com

commit c9cc8d01fb04117928830449388512a5047569c9 upstream.

If devpts_ptmx_path() returns an error code, then devpts_mntget() dereferences an ERR_PTR():

BUG: unable to handle kernel paging request at fffffffffffffff5 IP: devpts_mntget+0x13f/0x280 fs/devpts/inode.c:173

Fix it by returning early in the error paths.

Reproducer:

#define _GNU_SOURCE #include <fcntl.h> #include <sched.h> #include <sys/ioctl.h> #define TIOCGPTPEER _IO('T', 0x41)

int main() { for (;;) { int fd = open("/dev/ptmx", 0); unshare(CLONE_NEWNS); ioctl(fd, TIOCGPTPEER, 0); } }

Fixes: 311fc65c9fb9 ("pty: Repair TIOCGPTPEER") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- fs/devpts/inode.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/devpts/inode.c +++ b/fs/devpts/inode.c @@ -168,11 +168,11 @@ struct vfsmount *devpts_mntget(struct fi dput(path.dentry); if (err) { mntput(path.mnt); - path.mnt = ERR_PTR(err); + return ERR_PTR(err); } if (DEVPTS_SB(path.mnt->mnt_sb) != fsi) { mntput(path.mnt); - path.mnt = ERR_PTR(-ENODEV); + return ERR_PTR(-ENODEV); } return path.mnt; }

Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.14/pipe-fix-off-by-one-error-when-checking-buffer-limits.patch queue-4.14/crypto-hash-annotate-algorithms-taking-optional-key.patch queue-4.14/crypto-cryptd-pass-through-absence-of-setkey.patch queue-4.14/crypto-hash-prevent-using-keyed-hashes-without-setting-key.patch queue-4.14/ubifs-free-the-encrypted-symlink-target.patch queue-4.14/pipe-actually-allow-root-to-exceed-the-pipe-buffer-limits.patch queue-4.14/kernel-relay.c-revert-kernel-relay.c-fix-potential-memory-leak.patch queue-4.14/nfs-reject-request-for-id_legacy-key-without-auxdata.patch queue-4.14/crypto-poly1305-remove-setkey-method.patch queue-4.14/crypto-sha512-mb-initialize-pending-lengths-correctly.patch queue-4.14/devpts-fix-error-handling-in-devpts_mntget.patch queue-4.14/crypto-hash-introduce-crypto_hash_alg_has_setkey.patch queue-4.14/crypto-mcryptd-pass-through-absence-of-setkey.patch