In the Linux kernel, the following vulnerability has been resolved: rcu-tasks: Avoid pr_info() with spin lock in cblist_init_generic() pr_info() is called with rtp->cbs_gbl_lock spin lock locked. Because pr_info() calls printk() that might sleep, this will result in BUG like below: [ 0.206455] cblist_init_generic: Setting adjustable number of callback queues. [ 0.206463] [ 0.206464] ============================= [ 0.206464] [ BUG: Invalid wait context ] [ 0.206465] 5.19.0-00428-g9de1f9c8ca51 #5 Not tainted [ 0.206466] ----------------------------- [ 0.206466] swapper/0/1 is trying to lock: [ 0.206467] ffffffffa0167a58 (&port_lock_key){....}-{3:3}, at: serial8250_console_write+0x327/0x4a0 [ 0.206473] other info that might help us debug this: [ 0.206473] context-{5:5} [ 0.206474] 3 locks held by swapper/0/1: [ 0.206474] #0: ffffffff9eb597e0 (rcu_tasks.cbs_gbl_lock){....}-{2:2}, at: cblist_init_generic.constprop.0+0x14/0x1f0 [ 0.206478] #1: ffffffff9eb579c0 (console_lock){+.+.}-{0:0}, at: _printk+0x63/0x7e [ 0.206482] #2: ffffffff9ea77780 (console_owner){....}-{0:0}, at: console_emit_next_record.constprop.0+0x111/0x330 [ 0.206485] stack backtrace: [ 0.206486] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.19.0-00428-g9de1f9c8ca51 #5 [ 0.206488] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.fc36 04/01/2014 [ 0.206489] Call Trace: [ 0.206490] <TASK> [ 0.206491] dump_stack_lvl+0x6a/0x9f [ 0.206493] __lock_acquire.cold+0x2d7/0x2fe [ 0.206496] ? stack_trace_save+0x46/0x70 [ 0.206497] lock_acquire+0xd1/0x2f0 [ 0.206499] ? serial8250_console_write+0x327/0x4a0 [ 0.206500] ? __lock_acquire+0x5c7/0x2720 [ 0.206502] _raw_spin_lock_irqsave+0x3d/0x90 [ 0.206504] ? serial8250_console_write+0x327/0x4a0 [ 0.206506] serial8250_console_write+0x327/0x4a0 [ 0.206508] console_emit_next_record.constprop.0+0x180/0x330 [ 0.206511] console_unlock+0xf7/0x1f0 [ 0.206512] vprintk_emit+0xf7/0x330 [ 0.206514] _printk+0x63/0x7e [ 0.206516] cblist_init_generic.constprop.0.cold+0x24/0x32 [ 0.206518] rcu_init_tasks_generic+0x5/0xd9 [ 0.206522] kernel_init_freeable+0x15b/0x2a2 [ 0.206523] ? rest_init+0x160/0x160 [ 0.206526] kernel_init+0x11/0x120 [ 0.206527] ret_from_fork+0x1f/0x30 [ 0.206530] </TASK> [ 0.207018] cblist_init_generic: Setting shift to 1 and lim to 1. This patch moves pr_info() so that it is called without rtp->cbs_gbl_lock locked.
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