CVE-2026-31477ksmbd: fix memory leaks and NULL deref in smb2_lock()

Official description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix memory leaks and NULL deref in smb2_lock() smb2_lock() has three error handling issues after list_del() detaches smb_lock from lock_list at no_check_cl: 1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK path, goto out leaks smb_lock and its flock because the out: handler only iterates lock_list and rollback_list, neither of which contains the detached smb_lock. 2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out leaks smb_lock and flock for the same reason. The error code returned to the dispatcher is also stale. 3) In the rollback path, smb_flock_init() can return NULL on allocation failure. The result is dereferenced unconditionally, causing a kernel NULL pointer dereference. Add a NULL check to prevent the crash and clean up the bookkeeping; the VFS lock itself cannot be rolled back without the allocation and will be released at file or connection teardown. Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before the if(!rc) check in the UNLOCK branch so all exit paths share one free site, and by freeing smb_lock and flock before goto out in the non-UNLOCK branch. Propagate the correct error code in both cases. Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding a NULL check for locks_free_lock(rlock) in the shared cleanup. Found via call-graph analysis using sqry.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/cdac6f7e7e428dc70e3b5898ac6999a72ed13993
• https://git.kernel.org/stable/c/c9b95ef6f5039f19e46c3a521a4fe1752d91dfe9
• https://git.kernel.org/stable/c/91aeaa7256006d79a37298f5a1df23325db91599
• https://git.kernel.org/stable/c/3cdacd11b41569ce75b3162142240f2355e04900
• https://git.kernel.org/stable/c/aab42f0795620cf0d3955a520f571f697d0f9a2a
• https://git.kernel.org/stable/c/309b44ed684496ed3f9c5715d10b899338623512