bpf: backtracking shouldn't clear outer frame R1-R5 for callbacks
In the Linux kernel, the following vulnerability has been resolved: bpf: backtracking shouldn't clear outer frame R1-R5 for callbacks When processing calls to bpf_loop() verifier marks R1 (and R4) as precise. R1 tracks loop iterations number and because of the 'callback_depth < R1' mechanics in check_helper_call() must be marked precise. However, precision propagation for R1 was broken, when bpf_loop() call was verified on a second iteration. Consider the following verification trace: - main: bpf_loop(nr_loops, callback ...) - callback: BPF_EXIT - main: bpf_loop(nr_loops, callback ...) - ... While the first visit of the call to bpf_loop() propagated R1 precision as expected, the second call to mark_chain_precision() in the check_helper_call() set R1, but it was immediately reset when backtrack_insn() processed preceding BPF_EXIT in the loop deleted in this patch. Because of that, the second visit of the call to bpf_loop() injected checkpoint with R1 not marked as precise. Which could trick the verifier into accepting unsafe programs. See the next patch for an example of such program. Commit is structured in a way to minimize conflicts when 'bpf' would be eventually merged with 'bpf-next'.
CVE-2026-98084
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-2026-98084
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": "b43550d7d58e7ae6618aaab18c1e912fa4d6e3dd",
"lessThan": "1ac58dab0a83d2c64e3b807a3a0b399f17a74110",
"versionType": "git"
},
{
"status": "affected",
"version": "ab5cfac139ab8576fb54630d4cca23c3e690ee90",
"lessThan": "cdc93c6370f792d0649df2a145ac0cdcd430e411",
"versionType": "git"
},
{
"status": "affected",
"version": "ab5cfac139ab8576fb54630d4cca23c3e690ee90",
"lessThan": "3a39bc9707fbd1bef4df7318a9d02222741dda5b",
"versionType": "git"
},
{
"status": "affected",
"version": "ab5cfac139ab8576fb54630d4cca23c3e690ee90",
"lessThan": "f83890dfed9efc5e19df1dbc1ad707a142936923",
"versionType": "git"
},
{
"status": "affected",
"version": "ab5cfac139ab8576fb54630d4cca23c3e690ee90",
"lessThan": "e3e4f66cc4b72333d0886ae2673c360248987889",
"versionType": "git"
},
{
"status": "affected",
"version": "6.6.15",
"lessThan": "6.6.160",
"versionType": "semver"
}
],
"programFiles": [
"kernel/bpf/backtrack.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.7"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.7",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.114",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.57",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.7",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/backtrack.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98084
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #48849 · Revision 1
- Added to Heist Feed
- Publisher date