CVE-2026-89990

In the Linux kernel, the following vulnerability has been resolved:

ceph: lock mutex in cephmdscheck_access()

MDS session OPEN handling replaces mdsc->scapauths under

mdsc->mutex, freeing the previous array and its strings.

cephmdscheck_access() traverses this array without holding the

mutex.  A concurrent session reopen can therefore free the array while

it is being inspected, resulting in a use-after-free like this:

  Unable to handle kernel paging request at virtual address 003aaad64b2c8bb9

  [...]

  Internal error: Oops: 0000000096000004 [#1]  SMP

  Modules linked in:

  CPU: 56 UID: 2953037534 PID: 1253231 Comm: php-cgi8.4 Not tainted 6.18.45-i2-ampere #1146 NONE

  [..]

  pc : cephmdscheck_access+0xd4/0x550

  lr : cephmdscheck_access+0xc8/0x550

  [...]

  Call trace:

   cephmdscheck_access+0xd4/0x550 (P)

   cephatomicopen+0x138/0xbe8

   path_openat+0xa24/0xfa8

   dofilpopen+0x94/0x158

   dosysopenat2+0x88/0xf8