smb: Log an error when close_all_cached_dirs fails

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: smb: Log an error when close_all_cached_dirs fails Under low-memory conditions, close_all_cached_dirs() can't move the dentries to a separate list to dput() them once the locks are dropped. This will result in a "Dentry still in use" error, so add an error message that makes it clear this is what happened: [ 495.281119] CIFS: VFS: \\otters.example.com\share Out of memory while dropping dentries [ 495.281595] ------------[ cut here ]------------ [ 495.281887] BUG: Dentry ffff888115531138{i=78,n=/} still in use (2) [unmount of cifs cifs] [ 495.282391] WARNING: CPU: 1 PID: 2329 at fs/dcache.c:1536 umount_check+0xc8/0xf0 Also, bail out of looping through all tcons as soon as a single allocation fails, since we're already in trouble, and kmalloc() attempts for subseqeuent tcons are likely to fail just like the first one did.

References

• https://git.kernel.org/stable/c/b8ced2b9a23a1a2c1e0ed8d0d02512e51bdf38da
• https://git.kernel.org/stable/c/43f26094d6702e494e800532c3f1606e7a68eb30
• https://git.kernel.org/stable/c/4479db143390bdcadc1561292aab579cdfa9f6c6
• https://git.kernel.org/stable/c/a2182743a8b4969481f64aec4908ff162e8a206c