net: stmmac: fix integer underflow in chain mode

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Summary

CVECVE-2026-31649
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-24 15:16:44 UTC
Updated2026-04-24 17:51:40 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix integer underflow in chain mode The jumbo_frm() chain-mode implementation unconditionally computes len = nopaged_len - bmax; where nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is BUF_SIZE_8KiB or BUF_SIZE_2KiB. However, the caller stmmac_xmit() decides to invoke jumbo_frm() based on skb->len (total length including page fragments): is_jumbo = stmmac_is_jumbo_frm(priv, skb->len, enh_desc); When a packet has a small linear portion (nopaged_len <= bmax) but a large total length due to page fragments (skb->len > bmax), the subtraction wraps as an unsigned integer, producing a huge len value (~0xFFFFxxxx). This causes the while (len != 0) loop to execute hundreds of thousands of iterations, passing skb->data + bmax * i pointers far beyond the skb buffer to dma_map_single(). On IOMMU-less SoCs (the typical deployment for stmmac), this maps arbitrary kernel memory to the DMA engine, constituting a kernel memory disclosure and potential memory corruption from hardware. Fix this by introducing a buf_len local variable clamped to min(nopaged_len, bmax). Computing len = nopaged_len - buf_len is then always safe: it is zero when the linear portion fits within a single descriptor, causing the while (len != 0) loop to be skipped naturally, and the fragment loop in stmmac_xmit() handles page fragments afterward.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 513e06735f5be575b409d195822195348b164e48 git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 275bdf762e82082f064e60a92448fa2ac43cf95b git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 b7b8012193fd98236d7ae05d4b553f010a77b2ef git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 2c91b39912278d0878f9ba60ba04d2518b18a08d git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 6fca757c20396dc2e604dcc61922264e9e3dc803 git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 10d12b9240ebf96c785f0e2e4228318cd5f3a3eb git Not specified
CNA Linux Linux affected 286a837217204b1ef105e3a554d0757e4fdfaac1 51f4e090b9f87b40c21b6daadb5c06e6c0a07b67 git Not specified
CNA Linux Linux affected 3.2 Not specified
CNA Linux Linux unaffected 3.2 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.169 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.135 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.82 6.12.* 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/6fca757c20396dc2e604dcc61922264e9e3dc803 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/275bdf762e82082f064e60a92448fa2ac43cf95b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/513e06735f5be575b409d195822195348b164e48 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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