On Mon, Apr 26, 2021 at 09:29:20AM +0200, Greg Kroah-Hartman wrote:
From: Anirudh Rayabharam mail@anirudhrb.com
commit 8a12f8836145ffe37e9c8733dce18c22fb668b66 upstream
Multiple ttys try to claim the same the minor number causing a double unregistration of the same device. The first unregistration succeeds but the next one results in a null-ptr-deref.
The get_free_serial_index() function returns an available minor number but doesn't assign it immediately. The assignment is done by the caller later. But before this assignment, calls to get_free_serial_index() would return the same minor number.
Fix this by modifying get_free_serial_index to assign the minor number immediately after one is found to be and rename it to obtain_minor() to better reflect what it does. Similary, rename set_serial_by_index() to release_minor() and modify it to free up the minor number of the given hso_serial. Every obtain_minor() should have corresponding release_minor() call.
Fixes: 72dc1c096c705 ("HSO: add option hso driver") Reported-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com Tested-by: syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Anirudh Rayabharam mail@anirudhrb.com Signed-off-by: David S. Miller davem@davemloft.net [sudip: adjust context] Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
drivers/net/usb/hso.c | 33 ++++++++++++--------------------- 1 file changed, 12 insertions(+), 21 deletions(-)
We just got a regression report against this one. Perhaps better to hold off until that has been resolved.
https://lore.kernel.org/r/20210425233509.9ce29da49037e1a421000bdd@aruba.it
Johan