{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-26676", "modified": "2026-10-07T17:22:01Z", "upstream": [ "CVE-2024-26676" ], "published": "2024-04-02T07:02:26Z", "summary": "af_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC.", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC.\n\nsyzbot reported a warning [0] in __unix_gc() with a repro, which\ncreates a socketpair and sends one socket's fd to itself using the\npeer.\n\n socketpair(AF_UNIX, SOCK_STREAM, 0, [3, 4]) = 0\n sendmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base=\"\\360\", iov_len=1}],\n msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,\n cmsg_type=SCM_RIGHTS, cmsg_data=[3]}],\n msg_controllen=24, msg_flags=0}, MSG_OOB|MSG_PROBE|MSG_DONTWAIT|MSG_ZEROCOPY) = 1\n\nThis forms a self-cyclic reference that GC should finally untangle\nbut does not due to lack of MSG_OOB handling, resulting in memory\nleak.\n\nRecently, commit 11498715f266 (\"af_unix: Remove io_uring code for\nGC.\") removed io_uring's dead code in GC and revealed the problem.\n\nThe code was executed at the final stage of GC and unconditionally\nmoved all GC candidates from gc_candidates to gc_inflight_list.\nThat papered over the reported problem by always making the following\nWARN_ON_ONCE(!list_empty(&gc_candidates)) false.\n\nThe problem has been there since commit 2aab4b969002 (\"af_unix: fix\nstruct pid leaks in OOB support\") added full scm support for MSG_OOB\nwhile fixing another bug.\n\nTo fix this problem, we must call kfree_skb() for unix_sk(sk)->oob_skb\nif the socket still exists in gc_candidates after purging collected skb.\n\nThen, we need to set NULL to oob_skb before calling kfree_skb() because\nit calls last fput() and triggers unix_release_sock(), where we call\nduplicate kfree_skb(u->oob_skb) if not NULL.\n\nNote that the leaked socket remained being linked to a global list, so\nkmemleak also could not detect it. We need to check /proc/net/protocol\nto notice the unfreed socket.\n\n[0]:\nWARNING: CPU: 0 PID: 2863 at net/unix/garbage.c:345 __unix_gc+0xc74/0xe80 net/unix/garbage.c:345\nModules linked in:\nCPU: 0 PID: 2863 Comm: kworker/u4:11 Not tainted 6.8.0-rc1-syzkaller-00583-g1701940b1a02 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024\nWorkqueue: events_unbound __unix_gc\nRIP: 0010:__unix_gc+0xc74/0xe80 net/unix/garbage.c:345\nCode: 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 <0f> 0b 90 e9 7b fd ff ff 48 89 df e8 5c e7 7c f8 e9 d3 f8 ff ff e8\nRSP: 0018:ffffc9000b03fba0 EFLAGS: 00010293\nRAX: 0000000000000000 RBX: ffffc9000b03fc10 RCX: ffffffff816c493e\nRDX: ffff88802c02d940 RSI: ffffffff896982f3 RDI: ffffc9000b03fb30\nRBP: ffffc9000b03fce0 R08: 0000000000000001 R09: fffff52001607f66\nR10: 0000000000000003 R11: 0000000000000002 R12: dffffc0000000000\nR13: ffffc9000b03fc10 R14: ffffc9000b03fc10 R15: 0000000000000001\nFS: 0000000000000000(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000\nCS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00005559c8677a60 CR3: 000000000d57a000 CR4: 00000000003506f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n \n process_one_work+0x889/0x15e0 kernel/workqueue.c:2633\n process_scheduled_works kernel/workqueue.c:2706 [inline]\n worker_thread+0x8b9/0x12a0 kernel/workqueue.c:2787\n kthread+0x2c6/0x3b0 kernel/kthread.c:388\n ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242\n ", "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.21-1+rpt1", "1:6.1.47-1+rpt2", "1:6.1.47-1+rpt4", "1:6.1.54-1+rpt2", "1:6.1.58-1+rpt2", "1:6.1.63-1+rpt1", "1:6.1.73-1+rpt1" ], "ecosystem_specific": { 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"linux_commit": null, "upstream_version": "6.1.63", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.78" }, "1:6.1.73-1+rpt1": { "linux_commit": null, "upstream_version": "6.1.73", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.78" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2024-26676" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4fe505c63aa3273135a57597fda761e9aecc7668" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e0e09186d8821ad59806115d347ea32efa43ca4b" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/b74aa9ce13d02b7fd37c5325b99854f91b9b4276" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/82ae47c5c3a6b27fdc0f9e83c1499cb439c56140" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/1279f9d9dec2d7462823a18c29ad61359e0a007d" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-05-24T06:48:58Z" } }