ghsa-q4jh-g383-rjcg
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
net: implement lockless setsockopt(SO_PEEK_OFF)
syzbot reported a lockdep violation [1] involving af_unix support of SO_PEEK_OFF.
Since SO_PEEK_OFF is inherently not thread safe (it uses a per-socket sk_peek_off field), there is really no point to enforce a pointless thread safety in the kernel.
After this patch :
-
setsockopt(SO_PEEK_OFF) no longer acquires the socket lock.
-
skb_consume_udp() no longer has to acquire the socket lock.
-
af_unix no longer needs a special version of sk_set_peek_off(), because it does not lock u->iolock anymore.
As a followup, we could replace prot->set_peek_off to be a boolean and avoid an indirect call, since we always use sk_set_peek_off().
[1]
WARNING: possible circular locking dependency detected 6.8.0-rc4-syzkaller-00267-g0f1dd5e91e2b #0 Not tainted
syz-executor.2/30025 is trying to acquire lock: ffff8880765e7d80 (&u->iolock){+.+.}-{3:3}, at: unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789
but task is already holding lock: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline] ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1060 [inline] ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sk_setsockopt+0xe52/0x3360 net/core/sock.c:1193
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (sk_lock-AF_UNIX){+.+.}-{0:0}: lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 lock_sock_nested+0x48/0x100 net/core/sock.c:3524 lock_sock include/net/sock.h:1691 [inline] __unix_dgram_recvmsg+0x1275/0x12c0 net/unix/af_unix.c:2415 sock_recvmsg_nosec+0x18e/0x1d0 net/socket.c:1046 _sysrecvmsg+0x3c0/0x470 net/socket.c:2801 _sys_recvmsg net/socket.c:2845 [inline] do_recvmmsg+0x474/0xae0 net/socket.c:2939 __sys_recvmmsg net/socket.c:3018 [inline] __do_sys_recvmmsg net/socket.c:3041 [inline] __se_sys_recvmmsg net/socket.c:3034 [inline] __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3034 do_syscall_64+0xf9/0x240 entry_SYSCALL_64_after_hwframe+0x6f/0x77
-> #0 (&u->iolock){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869 __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137 lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789 sk_setsockopt+0x207e/0x3360 do_sock_setsockopt+0x2fb/0x720 net/socket.c:2307 __sys_setsockopt+0x1ad/0x250 net/socket.c:2334 __do_sys_setsockopt net/socket.c:2343 [inline] __se_sys_setsockopt net/socket.c:2340 [inline] __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340 do_syscall_64+0xf9/0x240 entry_SYSCALL_64_after_hwframe+0x6f/0x77
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(sk_lock-AF_UNIX); lock(&u->iolock); lock(sk_lock-AF_UNIX); lock(&u->iolock);
*** DEADLOCK ***
1 lock held by syz-executor.2/30025: #0: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline] #0: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1060 [inline] #0: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sk_setsockopt+0xe52/0x3360 net/core/sock.c:1193
stack backtrace: CPU: 0 PID: 30025 Comm: syz-executor.2 Not tainted 6.8.0-rc4-syzkaller-00267-g0f1dd5e91e2b #0 Hardware name: Google Google C ---truncated---
{
"affected": [],
"aliases": [
"CVE-2024-26732"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-04-03T17:15:50Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: implement lockless setsockopt(SO_PEEK_OFF)\n\nsyzbot reported a lockdep violation [1] involving af_unix\nsupport of SO_PEEK_OFF.\n\nSince SO_PEEK_OFF is inherently not thread safe (it uses a per-socket\nsk_peek_off field), there is really no point to enforce a pointless\nthread safety in the kernel.\n\nAfter this patch :\n\n- setsockopt(SO_PEEK_OFF) no longer acquires the socket lock.\n\n- skb_consume_udp() no longer has to acquire the socket lock.\n\n- af_unix no longer needs a special version of sk_set_peek_off(),\n because it does not lock u-\u003eiolock anymore.\n\nAs a followup, we could replace prot-\u003eset_peek_off to be a boolean\nand avoid an indirect call, since we always use sk_set_peek_off().\n\n[1]\n\nWARNING: possible circular locking dependency detected\n6.8.0-rc4-syzkaller-00267-g0f1dd5e91e2b #0 Not tainted\n\nsyz-executor.2/30025 is trying to acquire lock:\n ffff8880765e7d80 (\u0026u-\u003eiolock){+.+.}-{3:3}, at: unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789\n\nbut task is already holding lock:\n ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]\n ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1060 [inline]\n ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sk_setsockopt+0xe52/0x3360 net/core/sock.c:1193\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-\u003e #1 (sk_lock-AF_UNIX){+.+.}-{0:0}:\n lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754\n lock_sock_nested+0x48/0x100 net/core/sock.c:3524\n lock_sock include/net/sock.h:1691 [inline]\n __unix_dgram_recvmsg+0x1275/0x12c0 net/unix/af_unix.c:2415\n sock_recvmsg_nosec+0x18e/0x1d0 net/socket.c:1046\n ____sys_recvmsg+0x3c0/0x470 net/socket.c:2801\n ___sys_recvmsg net/socket.c:2845 [inline]\n do_recvmmsg+0x474/0xae0 net/socket.c:2939\n __sys_recvmmsg net/socket.c:3018 [inline]\n __do_sys_recvmmsg net/socket.c:3041 [inline]\n __se_sys_recvmmsg net/socket.c:3034 [inline]\n __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3034\n do_syscall_64+0xf9/0x240\n entry_SYSCALL_64_after_hwframe+0x6f/0x77\n\n-\u003e #0 (\u0026u-\u003eiolock){+.+.}-{3:3}:\n check_prev_add kernel/locking/lockdep.c:3134 [inline]\n check_prevs_add kernel/locking/lockdep.c:3253 [inline]\n validate_chain+0x18ca/0x58e0 kernel/locking/lockdep.c:3869\n __lock_acquire+0x1345/0x1fd0 kernel/locking/lockdep.c:5137\n lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754\n __mutex_lock_common kernel/locking/mutex.c:608 [inline]\n __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752\n unix_set_peek_off+0x26/0xa0 net/unix/af_unix.c:789\n sk_setsockopt+0x207e/0x3360\n do_sock_setsockopt+0x2fb/0x720 net/socket.c:2307\n __sys_setsockopt+0x1ad/0x250 net/socket.c:2334\n __do_sys_setsockopt net/socket.c:2343 [inline]\n __se_sys_setsockopt net/socket.c:2340 [inline]\n __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340\n do_syscall_64+0xf9/0x240\n entry_SYSCALL_64_after_hwframe+0x6f/0x77\n\nother info that might help us debug this:\n\n Possible unsafe locking scenario:\n\n CPU0 CPU1\n ---- ----\n lock(sk_lock-AF_UNIX);\n lock(\u0026u-\u003eiolock);\n lock(sk_lock-AF_UNIX);\n lock(\u0026u-\u003eiolock);\n\n *** DEADLOCK ***\n\n1 lock held by syz-executor.2/30025:\n #0: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]\n #0: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sockopt_lock_sock net/core/sock.c:1060 [inline]\n #0: ffff8880765e7930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sk_setsockopt+0xe52/0x3360 net/core/sock.c:1193\n\nstack backtrace:\nCPU: 0 PID: 30025 Comm: syz-executor.2 Not tainted 6.8.0-rc4-syzkaller-00267-g0f1dd5e91e2b #0\nHardware name: Google Google C\n---truncated---",
"id": "GHSA-q4jh-g383-rjcg",
"modified": "2024-04-03T18:30:41Z",
"published": "2024-04-03T18:30:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26732"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/56667da7399eb19af857e30f41bea89aa6fa812c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/897f75e2cde8a5f9f7529b55249af1fa4248c83b"
}
],
"schema_version": "1.4.0",
"severity": []
}