CVE-2026-89990

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CVE-2026-89990
In the Linux kernel, the following vulnerability has been resolved:

ceph: lock mutex in ceph_mds_check_access()

MDS session OPEN handling replaces mdsc->s_cap_auths under
mdsc->mutex, freeing the previous array and its strings.

ceph_mds_check_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 : ceph_mds_check_access+0xd4/0x550
lr : ceph_mds_check_access+0xc8/0x550
[...]
Call trace:
ceph_mds_check_access+0xd4/0x550 (P)
ceph_atomic_open+0x138/0xbe8
path_openat+0xa24/0xfa8
do_filp_open+0x94/0x158
do_sys_openat2+0x88/0xf8