From: Ludvig Michaelsson ludvig.michaelsson@yubico.com
commit 944ee77dc6ec7b0afd8ec70ffc418b238c92f12b upstream.
The hidraw_open() function increments the hidraw device reference counter. The counter has no dedicated synchronization mechanism, resulting in a potential data race when concurrently opening a device.
The race is a regression introduced by commit 8590222e4b02 ("HID: hidraw: Replace hidraw device table mutex with a rwsem"). While minors_rwsem is intended to protect the hidraw_table itself, by instead acquiring the lock for writing, the reference counter is also protected. This is symmetrical to hidraw_release().
Link: https://github.com/systemd/systemd/issues/27947 Fixes: 8590222e4b02 ("HID: hidraw: Replace hidraw device table mutex with a rwsem") Cc: stable@vger.kernel.org Signed-off-by: Ludvig Michaelsson ludvig.michaelsson@yubico.com Link: https://lore.kernel.org/r/20230621-hidraw-race-v1-1-a58e6ac69bab@yubico.com Signed-off-by: Benjamin Tissoires benjamin.tissoires@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/hid/hidraw.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/hid/hidraw.c +++ b/drivers/hid/hidraw.c @@ -272,7 +272,12 @@ static int hidraw_open(struct inode *ino goto out; }
- down_read(&minors_rwsem); + /* + * Technically not writing to the hidraw_table but a write lock is + * required to protect the device refcount. This is symmetrical to + * hidraw_release(). + */ + down_write(&minors_rwsem); if (!hidraw_table[minor] || !hidraw_table[minor]->exist) { err = -ENODEV; goto out_unlock; @@ -301,7 +306,7 @@ static int hidraw_open(struct inode *ino spin_unlock_irqrestore(&hidraw_table[minor]->list_lock, flags); file->private_data = list; out_unlock: - up_read(&minors_rwsem); + up_write(&minors_rwsem); out: if (err < 0) kfree(list);