The patch titled
Subject: mm/util.c: annotate an data race at vm_committed_as
has been added to the -mm tree. Its filename is
mm-util-annotate-an-data-race-at-vm_committed_as.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-util-annotate-an-data-race-at-vm_committed_as.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-util-annotate-an-data-race-at-vm_committed_as.patch
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------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: mm/util.c: annotate an data race at vm_committed_as
"vm_committed_as.count" could be accessed concurrently as reported by
KCSAN,
read to 0xffffffff923164f8 of 8 bytes by task 1268 on cpu 38:
__vm_enough_memory+0x43/0x280 mm/util.c:801
mmap_region+0x1b2/0xb90 mm/mmap.c:1726
do_mmap+0x45c/0x700
vm_mmap_pgoff+0xc0/0x130
vm_mmap+0x71/0x90
elf_map+0xa1/0x1b0
load_elf_binary+0x9de/0x2180
search_binary_handler+0xd8/0x2b0
__do_execve_file+0xb61/0x1080
__x64_sys_execve+0x5f/0x70
do_syscall_64+0x91/0xb47
entry_SYSCALL_64_after_hwframe+0x49/0xbe
write to 0xffffffff923164f8 of 8 bytes by task 1265 on cpu 41:
percpu_counter_add_batch+0x83/0xd0 lib/percpu_counter.c:91
exit_mmap+0x178/0x220 include/linux/mman.h:68
mmput+0x10e/0x270
flush_old_exec+0x572/0xfe0
load_elf_binary+0x467/0x2180
search_binary_handler+0xd8/0x2b0
__do_execve_file+0xb61/0x1080
__x64_sys_execve+0x5f/0x70
do_syscall_64+0x91/0xb47
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The warning is almost impossible to trigger according to the commit
82f71ae4a2b8 ("mm: catch memory commitment underflow") but leave it for
now to catch any possible unbalanced vm_unacct_memory() in the future.
Since only the read is operating as lockless, mark it as an intentional
data race using the data_race() macro to avoid modifying
percpu_counter_read() and still catch unintended races elsewhere.
Link: http://lkml.kernel.org/r/1581518109-21180-1-git-send-email-cai@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Acked-by: Dennis Zhou <dennis@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/util.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/mm/util.c~mm-util-annotate-an-data-race-at-vm_committed_as
+++ a/mm/util.c
@@ -798,8 +798,12 @@ int __vm_enough_memory(struct mm_struct
{
long allowed;
- VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
- -(s64)vm_committed_as_batch * num_online_cpus(),
+ /*
+ * A transient decrease in the value is unlikely, so no need
+ * READ_ONCE() for vm_committed_as.count.
+ */
+ VM_WARN_ONCE(data_race(percpu_counter_read(&vm_committed_as) <
+ -(s64)vm_committed_as_batch * num_online_cpus()),
"memory commitment underflow");
vm_acct_memory(pages);
_
Patches currently in -mm which might be from cai@xxxxxx are
mm-kmemleak-annotate-a-data-race-in-checksum.patch
mm-swapfile-fix-and-annotate-various-data-races.patch
mm-page_counter-fix-various-data-races-at-memsw.patch
mm-memcontrol-fix-a-data-race-in-scan-count.patch
mm-list_lru-fix-a-data-race-in-list_lru_count_one.patch
mm-mempool-fix-a-data-race-in-mempool_free.patch
mm-util-annotate-an-data-race-at-vm_committed_as.patch
mm-rmap-annotate-a-data-race-at-tlb_flush_batched.patch
mm-frontswap-mark-various-intentional-data-races.patch
mm-page_io-mark-various-intentional-data-races.patch
mm-swap_state-mark-various-intentional-data-races.patch
