kcm: fix zero-frag skb in frag_list on partial sendmsg error
In the Linux kernel, the following vulnerability has been resolved: kcm: fix zero-frag skb in frag_list on partial sendmsg error Syzkaller reported a warning in kcm_write_msgs() when processing a message with a zero-fragment skb in the frag_list. When kcm_sendmsg() fills MAX_SKB_FRAGS fragments in the current skb, it allocates a new skb (tskb) and links it into the frag_list before copying data. If the copy subsequently fails (e.g. -EFAULT from user memory), tskb remains in the frag_list with zero fragments: head skb (msg being assembled, NOT yet in sk_write_queue) +-----------+ | frags[17] | (MAX_SKB_FRAGS, all filled with data) | frag_list-+--> tskb +-----------+ +----------+ | frags[0] | (empty! copy failed before filling) +----------+ For SOCK_SEQPACKET with partial data already copied, the error path saves this message via partial_message for later completion. For SOCK_SEQPACKET, sock_write_iter() automatically sets MSG_EOR, so a subsequent zero-length write(fd, NULL, 0) completes the message and queues it to sk_write_queue. kcm_write_msgs() then walks the frag_list and hits: WARN_ON(!skb_shinfo(skb)->nr_frags) TCP has a similar pattern where skbs are enqueued before data copy and cleaned up on failure via tcp_remove_empty_skb(). KCM was missing the equivalent cleanup. Fix this by tracking the predecessor skb (frag_prev) when allocating a new frag_list entry. On error, if the tail skb has zero frags, use frag_prev to unlink and free it in O(1) without walking the singly-
CVE-2026-43244
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-2026-43244
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": "ab7ac4eb9832e32a09f4e8042705484d2fb0aad3",
"lessThan": "6f129a251c2795ba55dd5cc1fdf7e0af3098d848",
"versionType": "git"
},
{
"status": "affected",
"version": "ab7ac4eb9832e32a09f4e8042705484d2fb0aad3",
"lessThan": "9ea3671d70ee07480d80bebe86696397c4e99fb7",
"versionType": "git"
},
{
"status": "affected",
"version": "ab7ac4eb9832e32a09f4e8042705484d2fb0aad3",
"lessThan": "b1e3edf688a88c1a3ac41657055d9c136a08cd25",
"versionType": "git"
},
{
"status": "affected",
"version": "ab7ac4eb9832e32a09f4e8042705484d2fb0aad3",
"lessThan": "7af58f76e4b404a74c836881a845e6652db8a09f",
"versionType": "git"
},
{
"status": "affected",
"version": "ab7ac4eb9832e32a09f4e8042705484d2fb0aad3",
"lessThan": "ca220141fa8ebae09765a242076b2b77338106b0",
"versionType": "git"
}
],
"programFiles": [
"net/kcm/kcmsock.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.6"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.6",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.75",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.16",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "6.19.6",
"versionType": "semver",
"lessThanOrEqual": "6.19.*"
},
{
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/kcm/kcmsock.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-43244
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #46275 · Revision 1
- Added to Heist Feed
- Publisher date