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CVE-2025-38591

bpf: Reject narrower access to pointer ctx fields

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.249, 5.15.199, 6.1.162, 6.6.157, 6.12.67, and 1 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

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 __sk_buff. This access is detected as a narrower read in bpf_skb_is_valid_access because it doesn't match offsetof(struct __sk_buff, sk). It is therefore allowed and later proceeds to bpf_convert_ctx_access. Note that for the "is_narrower_load" case in the convert_ctx_accesses(), the insn->off is aligned, so the cnt may not be 0 because it matches the offsetof(struct __sk_buff, sk) in the bpf_convert_ctx_access. 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 sk_msg, sk_lookup, and sockopt) were also changed to use bpf_ctx_range_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 BPF_LOAD_ACQ instructions in insn_def_regno()"). Because syzbot somehow confused the two bugs, the new crash and repro didn't get reported to the mailing list.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in 7847c4140e06f6e87229faae22cc38525334c156; From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in feae34c992eb7191862fb1594c704fbbf650fef8; From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in 33660d44e789edb4f303210c813fc56d56377a90; From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in e2e9599f3503df7cf3569d2b6c50d5488fb59435; From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in 058a0da4f6d916a79b693384111bb80a90d73763; From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in 202900ceeef67458c964c2af6e1427c8e533ea7c; From f96da09473b52c09125cc9bf7d7d4576ae8229e0 · fixed in e09299225d5ba3916c91ef70565f7d2187e4cca0

  • Linux Linux

    4.13

  • KernelLinux

    From 4.13.0 · fixed in 5.10.249; From 5.11.0 · fixed in 5.15.199; From 5.16.0 · fixed in 6.1.162; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.67; From 6.13.0 · fixed in 6.16.1

References 7

git.kernel.org