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Subject[PATCH linux-next] kernel/fork.c: annotate data races for copy_process
Date
The check is only there to stop root fork bombs.

BUG: KCSAN: data-race in copy_process / copy_process

write to 0xffffffff86f87d20 of 4 bytes by task 7121 on cpu 5:
copy_process+0x2e1a/0x3af0 kernel/fork.c:2285
_do_fork+0xf7/0x790 kernel/fork.c:2430
__do_sys_clone+0xf9/0x130 kernel/fork.c:2585
__se_sys_clone kernel/fork.c:2566 [inline]
__x64_sys_clone+0x6c/0x80 kernel/fork.c:2566
do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff86f87d20 of 4 bytes by task 7125 on cpu 3:
copy_process+0x9eb/0x3af0 kernel/fork.c:1967
_do_fork+0xf7/0x790 kernel/fork.c:2430
__do_sys_clone+0xf9/0x130 kernel/fork.c:2585
__se_sys_clone kernel/fork.c:2566 [inline]
__x64_sys_clone+0x6c/0x80 kernel/fork.c:2566
do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Weilong Chen <chenweilong@huawei.com>
---
kernel/fork.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 142b23645d82..efc5493203ae 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1977,7 +1977,7 @@ static __latent_entropy struct task_struct *copy_process(
* to stop root fork bombs.
*/
retval = -EAGAIN;
- if (nr_threads >= max_threads)
+ if (data_race(nr_threads >= max_threads))
goto bad_fork_cleanup_count;

delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
--
2.17.1
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