CVE-2023-53813

/// Technical description

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

ext4: fix rbtree traversal bug in ext4_mb_use_preallocated

During allocations, while looking for preallocations(PA) in the per

inode rbtree, we can't do a direct traversal of the tree because

ext4_mb_discard_group_preallocation() can paralelly mark the pa deleted

and that can cause direct traversal to skip some entries. This was

leading to a BUG_ON() being hit [1] when we missed a PA that could satisfy

our request and ultimately tried to create a new PA that would overlap

with the missed one.

To makes sure we handle that case while still keeping the performance of

the rbtree, we make use of the fact that the only pa that could possibly

overlap the original goal start is the one that satisfies the below

conditions:

1. It must have it's logical start immediately to the left of

(ie less than) original logical start.

2. It must not be deleted

To find this pa we use the following traversal method:

1. Descend in

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References