The patch titled
Subject: fork: annotate a data race in vm_area_dup()
has been added to the -mm tree. Its filename is
fork-annotate-a-data-race-in-vm_area_dup.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fork-annotate-a-data-race-in-vm_area_dup.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fork-annotate-a-data-race-in-vm_area_dup.patch
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------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: fork: annotate a data race in vm_area_dup()
struct vm_area_struct could be accessed concurrently as noticed by
KCSAN,
write to 0xffff9cf8bba08ad8 of 8 bytes by task 14263 on cpu 35:
vma_interval_tree_insert+0x101/0x150:
rb_insert_augmented_cached at include/linux/rbtree_augmented.h:58
(inlined by) vma_interval_tree_insert at mm/interval_tree.c:23
__vma_link_file+0x6e/0xe0
__vma_link_file at mm/mmap.c:629
vma_link+0xa2/0x120
mmap_region+0x753/0xb90
do_mmap+0x45c/0x710
vm_mmap_pgoff+0xc0/0x130
ksys_mmap_pgoff+0x1d1/0x300
__x64_sys_mmap+0x33/0x40
do_syscall_64+0x91/0xc44
entry_SYSCALL_64_after_hwframe+0x49/0xbe
read to 0xffff9cf8bba08a80 of 200 bytes by task 14262 on cpu 122:
vm_area_dup+0x6a/0xe0
vm_area_dup at kernel/fork.c:362
__split_vma+0x72/0x2a0
__split_vma at mm/mmap.c:2661
split_vma+0x5a/0x80
mprotect_fixup+0x368/0x3f0
do_mprotect_pkey+0x263/0x420
__x64_sys_mprotect+0x51/0x70
do_syscall_64+0x91/0xc44
entry_SYSCALL_64_after_hwframe+0x49/0xbe
vm_area_dup() blindly copies all fields of original VMA to the new one.
This includes coping vm_area_struct::shared.rb which is normally protected
by i_mmap_lock. But this is fine because the read value will be
overwritten on the following __vma_link_file() under proper protection.
Thus, mark it as an intentional data race and insert a few assertions for
the fields that should not be modified concurrently.
Link: http://lkml.kernel.org/r/1582122495-12885-1-git-send-email-cai@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/kernel/fork.c~fork-annotate-a-data-race-in-vm_area_dup
+++ a/kernel/fork.c
@@ -359,7 +359,13 @@ struct vm_area_struct *vm_area_dup(struc
struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
if (new) {
- *new = *orig;
+ ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
+ ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
+ /*
+ * orig->shared.rb may be modified concurrently, but the clone
+ * will be reinitialized.
+ */
+ *new = data_race(*orig);
INIT_LIST_HEAD(&new->anon_vma_chain);
new->vm_next = new->vm_prev = NULL;
}
_
Patches currently in -mm which might be from cai@xxxxxx are
hugetlb_cgroup-add-interface-for-charge-uncharge-hugetlb-reservations-fix.patch
mm-frontswap-mark-various-intentional-data-races.patch
mm-page_io-mark-various-intentional-data-races.patch
mm-page_io-mark-various-intentional-data-races-v2.patch
mm-swap_state-mark-various-intentional-data-races.patch
mm-kmemleak-annotate-various-data-races-obj-ptr.patch
mm-swapfile-fix-and-annotate-various-data-races.patch
mm-swapfile-fix-and-annotate-various-data-races-v2.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
fork-annotate-a-data-race-in-vm_area_dup.patch
