GHSA-C7GR-CRGH-PWCP
Vulnerability from github – Published: 2025-03-17 18:31 – Updated: 2025-03-17 18:31In the Linux kernel, the following vulnerability has been resolved:
tty: fix deadlock caused by calling printk() under tty_port->lock
pty_write() invokes kmalloc() which may invoke a normal printk() to print failure message. This can cause a deadlock in the scenario reported by syz-bot below:
CPU0 CPU1 CPU2
---- ---- ----
lock(console_owner);
lock(&port_lock_key);
lock(&port->lock); lock(&port_lock_key); lock(&port->lock); lock(console_owner);
As commit dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") said, such deadlock can be prevented by using printk_deferred() in kmalloc() (which is invoked in the section guarded by the port->lock). But there are too many printk() on the kmalloc() path, and kmalloc() can be called from anywhere, so changing printk() to printk_deferred() is too complicated and inelegant.
Therefore, this patch chooses to specify __GFP_NOWARN to kmalloc(), so that printk() will not be called, and this deadlock problem can be avoided.
Syzbot reported the following lockdep error:
====================================================== WARNING: possible circular locking dependency detected 5.4.143-00237-g08ccc19a-dirty #10 Not tainted
syz-executor.4/29420 is trying to acquire lock: ffffffff8aedb2a0 (console_owner){....}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1752 [inline] ffffffff8aedb2a0 (console_owner){....}-{0:0}, at: vprintk_emit+0x2ca/0x470 kernel/printk/printk.c:2023
but task is already holding lock: ffff8880119c9158 (&port->lock){-.-.}-{2:2}, at: pty_write+0xf4/0x1f0 drivers/tty/pty.c:120
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&port->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159 tty_port_tty_get drivers/tty/tty_port.c:288 [inline] <-- lock(&port->lock); tty_port_default_wakeup+0x1d/0xb0 drivers/tty/tty_port.c:47 serial8250_tx_chars+0x530/0xa80 drivers/tty/serial/8250/8250_port.c:1767 serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1854 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1827 [inline] <-- lock(&port_lock_key); serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1870 serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x109/0xa50 kernel/irq/handle.c:156 [...]
-> #1 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159 serial8250_console_write+0x184/0xa40 drivers/tty/serial/8250/8250_port.c:3198 <-- lock(&port_lock_key); call_console_drivers kernel/printk/printk.c:1819 [inline] console_unlock+0x8cb/0xd00 kernel/printk/printk.c:2504 vprintk_emit+0x1b5/0x470 kernel/printk/printk.c:2024 <-- lock(console_owner); vprintk_func+0x8d/0x250 kernel/printk/printk_safe.c:394 printk+0xba/0xed kernel/printk/printk.c:2084 register_console+0x8b3/0xc10 kernel/printk/printk.c:2829 univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:681 console_init+0x49d/0x6d3 kernel/printk/printk.c:2915 start_kernel+0x5e9/0x879 init/main.c:713 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241
-> #0 (console_owner){....}-{0:0}: [...] lock_acquire+0x127/0x340 kernel/locking/lockdep.c:4734 console_trylock_spinning kernel/printk/printk.c:1773 ---truncated---
{
"affected": [],
"aliases": [
"CVE-2022-49441"
],
"database_specific": {
"cwe_ids": [
"CWE-667"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-26T07:01:20Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntty: fix deadlock caused by calling printk() under tty_port-\u003elock\n\npty_write() invokes kmalloc() which may invoke a normal printk() to print\nfailure message. This can cause a deadlock in the scenario reported by\nsyz-bot below:\n\n CPU0 CPU1 CPU2\n ---- ---- ----\n lock(console_owner);\n lock(\u0026port_lock_key);\n lock(\u0026port-\u003elock);\n lock(\u0026port_lock_key);\n lock(\u0026port-\u003elock);\n lock(console_owner);\n\nAs commit dbdda842fe96 (\"printk: Add console owner and waiter logic to\nload balance console writes\") said, such deadlock can be prevented by\nusing printk_deferred() in kmalloc() (which is invoked in the section\nguarded by the port-\u003elock). But there are too many printk() on the\nkmalloc() path, and kmalloc() can be called from anywhere, so changing\nprintk() to printk_deferred() is too complicated and inelegant.\n\nTherefore, this patch chooses to specify __GFP_NOWARN to kmalloc(), so\nthat printk() will not be called, and this deadlock problem can be\navoided.\n\nSyzbot reported the following lockdep error:\n\n======================================================\nWARNING: possible circular locking dependency detected\n5.4.143-00237-g08ccc19a-dirty #10 Not tainted\n------------------------------------------------------\nsyz-executor.4/29420 is trying to acquire lock:\nffffffff8aedb2a0 (console_owner){....}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1752 [inline]\nffffffff8aedb2a0 (console_owner){....}-{0:0}, at: vprintk_emit+0x2ca/0x470 kernel/printk/printk.c:2023\n\nbut task is already holding lock:\nffff8880119c9158 (\u0026port-\u003elock){-.-.}-{2:2}, at: pty_write+0xf4/0x1f0 drivers/tty/pty.c:120\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-\u003e #2 (\u0026port-\u003elock){-.-.}-{2:2}:\n __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]\n _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159\n tty_port_tty_get drivers/tty/tty_port.c:288 [inline] \t\t\u003c-- lock(\u0026port-\u003elock);\n tty_port_default_wakeup+0x1d/0xb0 drivers/tty/tty_port.c:47\n serial8250_tx_chars+0x530/0xa80 drivers/tty/serial/8250/8250_port.c:1767\n serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1854\n serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1827 [inline] \t\u003c-- lock(\u0026port_lock_key);\n serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1870\n serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126\n __handle_irq_event_percpu+0x109/0xa50 kernel/irq/handle.c:156\n [...]\n\n-\u003e #1 (\u0026port_lock_key){-.-.}-{2:2}:\n __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]\n _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159\n serial8250_console_write+0x184/0xa40 drivers/tty/serial/8250/8250_port.c:3198\n\t\t\t\t\t\t\t\t\t\t\u003c-- lock(\u0026port_lock_key);\n call_console_drivers kernel/printk/printk.c:1819 [inline]\n console_unlock+0x8cb/0xd00 kernel/printk/printk.c:2504\n vprintk_emit+0x1b5/0x470 kernel/printk/printk.c:2024\t\t\t\u003c-- lock(console_owner);\n vprintk_func+0x8d/0x250 kernel/printk/printk_safe.c:394\n printk+0xba/0xed kernel/printk/printk.c:2084\n register_console+0x8b3/0xc10 kernel/printk/printk.c:2829\n univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:681\n console_init+0x49d/0x6d3 kernel/printk/printk.c:2915\n start_kernel+0x5e9/0x879 init/main.c:713\n secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241\n\n-\u003e #0 (console_owner){....}-{0:0}:\n [...]\n lock_acquire+0x127/0x340 kernel/locking/lockdep.c:4734\n console_trylock_spinning kernel/printk/printk.c:1773 \n---truncated---",
"id": "GHSA-c7gr-crgh-pwcp",
"modified": "2025-03-17T18:31:47Z",
"published": "2025-03-17T18:31:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-49441"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/04ee31678c128a6cc7bb057ea189a8624ba5a314"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0bcf44903ef4df742dcada86ccaedd25374ffb50"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/18ca0d55e8639b911df8aae1b47598b13f9acded"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3219ac364ac3d8d30771612a6010f1e0b7fa0a28"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4af21b12a60ed2d3642284f4f85b42d7dc6ac246"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4c253caf9264d2aa47ee806a87986dd8eb91a5d9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6b9dbedbe3499fef862c4dff5217cf91f34e43b3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9834b13e8b962caa28fbcf1f422dd82413da4ede"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b3c974501d0c32258ae0e04e5cc3fb92383b40f6"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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