bpf: Reject narrower access to pointer ctx fields
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.
CVE-2025-38591
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-38591
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "7847c4140e06f6e87229faae22cc38525334c156",
"versionType": "git"
},
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "feae34c992eb7191862fb1594c704fbbf650fef8",
"versionType": "git"
},
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "33660d44e789edb4f303210c813fc56d56377a90",
"versionType": "git"
},
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "e2e9599f3503df7cf3569d2b6c50d5488fb59435",
"versionType": "git"
},
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "058a0da4f6d916a79b693384111bb80a90d73763",
"versionType": "git"
},
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "202900ceeef67458c964c2af6e1427c8e533ea7c",
"versionType": "git"
},
{
"status": "affected",
"version": "f96da09473b52c09125cc9bf7d7d4576ae8229e0",
"lessThan": "e09299225d5ba3916c91ef70565f7d2187e4cca0",
"versionType": "git"
}
],
"programFiles": [
"kernel/bpf/cgroup.c",
"net/core/filter.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.13"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.13",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.249",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.199",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.162",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.67",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.16.1",
"versionType": "semver",
"lessThanOrEqual": "6.16.*"
},
{
"status": "unaffected",
"version": "6.17",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/cgroup.c",
"net/core/filter.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-38591
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #27043 · Revision 1
- Added to Heist Feed
- Publisher date