The patch titled
Subject: prctl: add comment about mmap_sem and arg_lock
has been added to the -mm tree. Its filename is
mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix.patch
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------------------------------------------------------
From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Subject: prctl: add comment about mmap_sem and arg_lock
add comment to elaborate why mmap_sem for is used by prctl
Link: http://lkml.kernel.org/r/1524077799-80690-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mateusz Guzik <mguzik@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sys.c | 4 ++++
1 file changed, 4 insertions(+)
diff -puN kernel/sys.c~mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix kernel/sys.c
--- a/kernel/sys.c~mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix
+++ a/kernel/sys.c
@@ -2011,6 +2011,10 @@ static int prctl_set_mm_map(int opt, con
return error;
}
+ /*
+ * arg_lock protects concurent updates but we still need mmap_sem for
+ * read to exclude races with sys_brk.
+ */
down_read(&mm->mmap_sem);
/*
_
Patches currently in -mm which might be from yang.shi@xxxxxxxxxxxxxxxxx are
mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct.patch
mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix.patch
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