Bug 2365241 (CVE-2025-37879)

Summary: CVE-2025-37879 kernel: 9p/net: fix improper handling of bogus negative read/write replies
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
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Hardware: All   
OS: Linux   
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Description OSIDB Bzimport 2025-05-09 07:01:18 UTC 
In the Linux kernel, the following vulnerability has been resolved:

9p/net: fix improper handling of bogus negative read/write replies

In p9_client_write() and p9_client_read_once(), if the server
incorrectly replies with success but a negative write/read count then we
would consider written (negative) <= rsize (positive) because both
variables were signed.

Make variables unsigned to avoid this problem.

The reproducer linked below now fails with the following error instead
of a null pointer deref:
9pnet: bogus RWRITE count (4294967295 > 3)
Comment 1 Michal Findra 2025-05-09 09:31:13 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025050943-CVE-2025-37879-a59f@gregkh/T