On Tue, Jan 04, 2022 at 05:29:34PM -0500, Jeffrey E Altman wrote:

Please backport commit 0dc54bd4d6e03be1f0b678c4297170b79f1a44ab ("fscache_cookie_enabled: check cookie is valid before accessing it") to the 5.13, 5.14, and 5.15 kernel series.

Only 5.15 is still alive, see the front page of kernel.org to see the active kernel verisons.

Commit 0dc54bd4d6e03be1f0b678c4297170b79f1a44ab fixes a bug introduced by 3003bbd0697b659944237f3459489cb596ba196c ("afs: Use the netfs_write_begin() helper") that results in a NULL pointer dereference observed in Fedora 35 when accessing afs volumes from Kubernetes.

[ 3627.403829] BUG: kernel NULL pointer dereference, address: 0000000000000068 [ 3627.411649] RIP: 0010:afs_is_cache_enabled+0xc/0x30 [kafs] [ 3627.419900] Call Trace: [ 3627.420432]  <TASK> [ 3627.420957]  netfs_write_begin+0x1ff/0x810 [netfs] [ 3627.421498]  ? lock_timer_base+0x61/0x80 [ 3627.422124]  afs_write_begin+0x58/0x240 [kafs] [ 3627.422738]  generic_perform_write+0xae/0x1d0 [ 3627.423325]  ? file_update_time+0xd2/0x120 [ 3627.423806]  __generic_file_write_iter+0x101/0x1d0 [ 3627.424275]  generic_file_write_iter+0x5d/0xb0 [ 3627.424741]  afs_file_write+0x73/0xa0 [kafs] [ 3627.425270]  new_sync_write+0x10b/0x180 [ 3627.425708]  vfs_write+0x1ce/0x260 [ 3627.426160]  ksys_write+0x4f/0xc0 [ 3627.426606]  do_syscall_64+0x3b/0x90 [ 3627.427086]  entry_SYSCALL_64_after_hwframe+0x44/0xae

The defect was introduced in v5.13-rc1 and fixed in v5.16-rc1.

Now queued up, thanks.

greg k-h