CVE-2023-53231

In the Linux kernel, the following vulnerability has been resolved:

erofs: Fix detection of atomic context

Current check for atomic context is not sufficient as

z_erofs_decompressqueue_endio can be called under rcu lock

from blk_mq_flush_plug_list(). See the stacktrace [1]

In such case we should hand off the decompression work for async

processing rather than trying to do sync decompression in current

context. Patch fixes the detection by checking for

rcu_read_lock_any_held() and while at it use more appropriate

!in_task() check than in_atomic().

Background: Historically erofs would always schedule a kworker for

decompression which would incur the scheduling cost regardless of

the context. But z_erofs_decompressqueue_endio() may not always

be in atomic context and we could actually benefit from doing the

decompression in z_erofs_decompressqueue_endio() if we are in

thread context, for example when running with dm-verity.

This optimization was later added in patch [2] which has shown

improvement in performance benchmarks.

==============================================

[1] Problem stacktrace

[name:core&]BUG: sleeping function called from invalid context at kernel/locking/mutex.c:291

[name:core&]in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 1615, name: CpuMonitorServi

[name:core&]preempt_count: 0, expected: 0

[name:core&]RCU nest depth: 1, expected: 0

CPU: 7 PID: 1615 Comm: CpuMonitorServi Tainted: G S W OE 6.1.25-android14-5-maybe-dirty-mainline #1

Hardware name: MT6897 (DT)

Call trace:

dump_backtrace+0x108/0x15c

show_stack+0x20/0x30

dump_stack_lvl+0x6c/0x8c

dump_stack+0x20/0x48

__might_resched+0x1fc/0x308

__might_sleep+0x50/0x88

mutex_lock+0x2c/0x110

z_erofs_decompress_queue+0x11c/0xc10

z_erofs_decompress_kickoff+0x110/0x1a4

z_erofs_decompressqueue_endio+0x154/0x180

bio_endio+0x1b0/0x1d8

__dm_io_complete+0x22c/0x280

clone_endio+0xe4/0x280

bio_endio+0x1b0/0x1d8

blk_update_request+0x138/0x3a4

blk_mq_plug_issue_direct+0xd4/0x19c

blk_mq_flush_plug_list+0x2b0/0x354

__blk_flush_plug+0x110/0x160

blk_finish_plug+0x30/0x4c

read_pages+0x2fc/0x370

page_cache_ra_unbounded+0xa4/0x23c

page_cache_ra_order+0x290/0x320

do_sync_mmap_readahead+0x108/0x2c0

filemap_fault+0x19c/0x52c

__do_fault+0xc4/0x114

handle_mm_fault+0x5b4/0x1168

do_page_fault+0x338/0x4b4

do_translation_fault+0x40/0x60

do_mem_abort+0x60/0xc8

el0_da+0x4c/0xe0

el0t_64_sync_handler+0xd4/0xfc

el0t_64_sync+0x1a0/0x1a4

[2] Link: https://lore.kernel.org/all/[email protected]/