CVE-2025-38591
- Source
- https://nvd.nist.gov/vuln/detail/CVE-2025-38591
- Import Source
- https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-38591.json
- JSON Data
- https://api.test.osv.dev/v1/vulns/CVE-2025-38591
- Downstream
- Related
- Published
- 2025-08-19T17:03:12Z
- Modified
- 2025-10-18T05:06:55.306046Z
- Summary
- bpf: Reject narrower access to pointer ctx fields
- Details
-
In the Linux kernel, the following vulnerability has been resolved:
bpf: Reject narrower access to pointer ctx fields
The following BPF program, simplified from a syzkaller repro, causes a kernel warning:
r0 = *(u8 *)(r1 + 169); exit;With pointer field sk being at offset 168 in _skbuff. This access is detected as a narrower read in bpfskbisvalidaccess because it doesn't match offsetof(struct _skbuff, sk). It is therefore allowed and later proceeds to bpfconvertctxaccess. Note that for the "isnarrowerload" case in the convertctxaccesses(), the insn->off is aligned, so the cnt may not be 0 because it matches the offsetof(struct _skbuff, sk) in the bpfconvertctxaccess. However, the target_size stays 0 and the verifier errors with a kernel warning:
verifier bug: error during ctx access conversion(1)This patch fixes that to return a proper "invalid bpf_context access off=X size=Y" error on the load instruction.
The same issue affects multiple other fields in context structures that allow narrow access. Some other non-affected fields (for skmsg, sklookup, and sockopt) were also changed to use bpfctxrange_ptr for consistency.
Note this syzkaller crash was reported in the "Closes" link below, which used to be about a different bug, fixed in commit fce7bd8e385a ("bpf/verifier: Handle BPFLOADACQ instructions in insndefregno()"). Because syzbot somehow confused the two bugs, the new crash and repro didn't get reported to the mailing list.
- References
Affected packages
Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Affected ranges
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introducedf96da09473b52c09125cc9bf7d7d4576ae8229e0Fixed202900ceeef67458c964c2af6e1427c8e533ea7c
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introducedf96da09473b52c09125cc9bf7d7d4576ae8229e0Fixede09299225d5ba3916c91ef70565f7d2187e4cca0