In the Linux kernel, the following vulnerability has been resolved: libceph: Fix potential out-of-bounds access in crush_decode() A message of type CEPH_MSG_OSD_MAP containing a crush map with at least one bucket has two fields holding the bucket algorithm. If the values in these two fields differ, an out-of-bounds access can occur. This is the case because the first algorithm field (alg) is used to allocate the correct amount of memory for a bucket of this type, while the second algorithm field inside the bucket (b->alg) is used in the subsequent processing. This patch fixes the issue by adding a check that compares alg and b->alg and aborts the processing in case they differ. Furthermore, b->alg is set to 0 in this case, because the destruction of the crush map also uses this field to determine the bucket type, which can again result in an out-of-bounds access when trying to free the memory pointed to by the fields of the bucket. To correctly free the memory allocated for the bucket in such a case, the corresponding call to kfree is moved from the algorithm-specific crush_destroy_bucket functions to the generic crush_destroy_bucket().
A CEPH_MSG_OSD_MAP message containing a CRUSH map with at least one bucket has two fields storing the bucket algorithm. The first field (alg) is used to allocate the appropriate amount of memory for a given bucket type, while the second field within the bucket (b->alg) is applied in the next processing stage. When the values of these two fields differ, out-of-bounds memory access occurs — both during processing and during memory deallocation attempts (CRUSH map destruction also uses the b->alg field to determine bucket type). The patch adds verification of both field consistency and zeros b->alg in case of mismatch, and the kfree call has been moved to a generic crush_destroy_bucket() function.
A remote attacker, without authentication, can trigger out-of-bounds memory access, potentially leading to disclosure of sensitive data, memory corruption, and consequently to system compromise or destabilization.
Apply patches available from the vendor according to references — fixes have been published in the Linux kernel stable repository and are available at the addresses indicated in the references section
Linux kernel with libceph component — specific versions indicated in vendor references (commits in the stable kernel.org repository)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H