{"id":"DEBIAN-CVE-2024-26676","details":"In the Linux kernel, the following vulnerability has been resolved:  af_unix: Call kfree_skb() for dead unix_(sk)-\u003eoob_skb in GC.  syzbot reported a warning [0] in __unix_gc() with a repro, which creates a socketpair and sends one socket's fd to itself using the peer.    socketpair(AF_UNIX, SOCK_STREAM, 0, [3, 4]) = 0   sendmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base=\"\\360\", iov_len=1}],           msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,                                       cmsg_type=SCM_RIGHTS, cmsg_data=[3]}],           msg_controllen=24, msg_flags=0}, MSG_OOB|MSG_PROBE|MSG_DONTWAIT|MSG_ZEROCOPY) = 1  This forms a self-cyclic reference that GC should finally untangle but does not due to lack of MSG_OOB handling, resulting in memory leak.  Recently, commit 11498715f266 (\"af_unix: Remove io_uring code for GC.\") removed io_uring's dead code in GC and revealed the problem.  The code was executed at the final stage of GC and unconditionally moved all GC candidates from gc_candidates to gc_inflight_list. That papered over the reported problem by always making the following WARN_ON_ONCE(!list_empty(&gc_candidates)) false.  The problem has been there since commit 2aab4b969002 (\"af_unix: fix struct pid leaks in OOB support\") added full scm support for MSG_OOB while fixing another bug.  To fix this problem, we must call kfree_skb() for unix_sk(sk)-\u003eoob_skb if the socket still exists in gc_candidates after purging collected skb.  Then, we need to set NULL to oob_skb before calling kfree_skb() because it calls last fput() and triggers unix_release_sock(), where we call duplicate kfree_skb(u-\u003eoob_skb) if not NULL.  Note that the leaked socket remained being linked to a global list, so kmemleak also could not detect it.  We need to check /proc/net/protocol to notice the unfreed socket.  [0]: WARNING: CPU: 0 PID: 2863 at net/unix/garbage.c:345 __unix_gc+0xc74/0xe80 net/unix/garbage.c:345 Modules linked in: CPU: 0 PID: 2863 Comm: kworker/u4:11 Not tainted 6.8.0-rc1-syzkaller-00583-g1701940b1a02 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 Workqueue: events_unbound __unix_gc RIP: 0010:__unix_gc+0xc74/0xe80 net/unix/garbage.c:345 Code: 8b 5c 24 50 e9 86 f8 ff ff e8 f8 e4 22 f8 31 d2 48 c7 c6 30 6a 69 89 4c 89 ef e8 97 ef ff ff e9 80 f9 ff ff e8 dd e4 22 f8 90 \u003c0f\u003e 0b 90 e9 7b fd ff ff 48 89 df e8 5c e7 7c f8 e9 d3 f8 ff ff e8 RSP: 0018:ffffc9000b03fba0 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffffc9000b03fc10 RCX: ffffffff816c493e RDX: ffff88802c02d940 RSI: ffffffff896982f3 RDI: ffffc9000b03fb30 RBP: ffffc9000b03fce0 R08: 0000000000000001 R09: fffff52001607f66 R10: 0000000000000003 R11: 0000000000000002 R12: dffffc0000000000 R13: ffffc9000b03fc10 R14: ffffc9000b03fc10 R15: 0000000000000001 FS:  0000000000000000(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005559c8677a60 CR3: 000000000d57a000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace:  \u003cTASK\u003e  process_one_work+0x889/0x15e0 kernel/workqueue.c:2633  process_scheduled_works kernel/workqueue.c:2706 [inline]  worker_thread+0x8b9/0x12a0 kernel/workqueue.c:2787  kthread+0x2c6/0x3b0 kernel/kthread.c:388  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147  ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242  \u003c/TASK\u003e","modified":"2026-09-15T09:03:04.994049594Z","published":"2024-04-02T07:15:44.170Z","upstream":["CVE-2024-26676"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-26676"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.82-1"}]}],"versions":["6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26676.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.7.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26676.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.7.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26676.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}