rxrpc: Fix RxGK token loading to check bounds

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Summary

CVECVE-2026-31641
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-24 15:16:43 UTC
Updated2026-04-24 17:51:40 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix RxGK token loading to check bounds rxrpc_preparse_xdr_yfs_rxgk() reads the raw key length and ticket length from the XDR token as u32 values and passes each through round_up(x, 4) before using the rounded value for validation and allocation. When the raw length is >= 0xfffffffd, round_up() wraps to 0, so the bounds check and kzalloc both use 0 while the subsequent memcpy still copies the original ~4 GiB value, producing a heap buffer overflow reachable from an unprivileged add_key() call. Fix this by: (1) Rejecting raw key lengths above AFSTOKEN_GK_KEY_MAX and raw ticket lengths above AFSTOKEN_GK_TOKEN_MAX before rounding, consistent with the caps that the RxKAD path already enforces via AFSTOKEN_RK_TIX_MAX. (2) Sizing the flexible-array allocation from the validated raw key length via struct_size_t() instead of the rounded value. (3) Caching the raw lengths so that the later field assignments and memcpy calls do not re-read from the token, eliminating a class of TOCTOU re-parse. The control path (valid token with lengths within bounds) is unaffected.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 0ca100ff4df64f5d0f6c1dd5080c3e096786bea6 3e04596cba8a86cbff9c3f4bf0a524a3a488773c git Not specified
CNA Linux Linux affected 0ca100ff4df64f5d0f6c1dd5080c3e096786bea6 49875b360c2b83a3c226e189c502e501d83e6445 git Not specified
CNA Linux Linux affected 0ca100ff4df64f5d0f6c1dd5080c3e096786bea6 d179a868dd755b0cfcf7582e00943d702b9943b8 git Not specified
CNA Linux Linux affected 6.16 Not specified
CNA Linux Linux unaffected 6.16 semver Not specified
CNA Linux Linux unaffected 6.18.23 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.13 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/d179a868dd755b0cfcf7582e00943d702b9943b8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/49875b360c2b83a3c226e189c502e501d83e6445 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3e04596cba8a86cbff9c3f4bf0a524a3a488773c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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