Bug 2338193 (CVE-2024-57892)

Summary: CVE-2024-57892 kernel: ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: high    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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OS: Linux   
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Description OSIDB Bzimport 2025-01-15 14:02:22 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv

When mounting ocfs2 and then remounting it as read-only, a
slab-use-after-free occurs after the user uses a syscall to
quota_getnextquota.  Specifically, sb_dqinfo(sb, type)->dqi_priv is the
dangling pointer.

During the remounting process, the pointer dqi_priv is freed but is never
set as null leaving it to be accessed.  Additionally, the read-only option
for remounting sets the DQUOT_SUSPENDED flag instead of setting the
DQUOT_USAGE_ENABLED flags.  Moreover, later in the process of getting the
next quota, the function ocfs2_get_next_id is called and only checks the
quota usage flags and not the quota suspended flags.

To fix this, I set dqi_priv to null when it is freed after remounting with
read-only and put a check for DQUOT_SUSPENDED in ocfs2_get_next_id.

[akpm: coding-style cleanups]
Comment 1 Mauro Matteo Cascella 2025-01-15 14:19:59 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025011513-CVE-2024-57892-6d53@gregkh/T