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Subject[PATCH 4.19 025/109] mm/memory-failure: make sure wait for page writeback in memory_failure
Date
From: yangerkun <yangerkun@huawei.com>

[ Upstream commit e8675d291ac007e1c636870db880f837a9ea112a ]

Our syzkaller trigger the "BUG_ON(!list_empty(&inode->i_wb_list))" in
clear_inode:

kernel BUG at fs/inode.c:519!
Internal error: Oops - BUG: 0 [#1] SMP
Modules linked in:
Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)
CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95
Hardware name: linux,dummy-virt (DT)
pstate: 80000005 (Nzcv daif -PAN -UAO)
pc : clear_inode+0x280/0x2a8
lr : clear_inode+0x280/0x2a8
Call trace:
clear_inode+0x280/0x2a8
ext4_clear_inode+0x38/0xe8
ext4_free_inode+0x130/0xc68
ext4_evict_inode+0xb20/0xcb8
evict+0x1a8/0x3c0
iput+0x344/0x460
do_unlinkat+0x260/0x410
__arm64_sys_unlinkat+0x6c/0xc0
el0_svc_common+0xdc/0x3b0
el0_svc_handler+0xf8/0x160
el0_svc+0x10/0x218
Kernel panic - not syncing: Fatal exception

A crash dump of this problem show that someone called __munlock_pagevec
to clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap
-> munlock_vma_pages_range -> __munlock_pagevec.

As a result memory_failure will call identify_page_state without
wait_on_page_writeback. And after truncate_error_page clear the mapping
of this page. end_page_writeback won't call sb_clear_inode_writeback to
clear inode->i_wb_list. That will trigger BUG_ON in clear_inode!

Fix it by checking PageWriteback too to help determine should we skip
wait_on_page_writeback.

Link: https://lkml.kernel.org/r/20210604084705.3729204-1-yangerkun@huawei.com
Fixes: 0bc1f8b0682c ("hwpoison: fix the handling path of the victimized page frame that belong to non-LRU")
Signed-off-by: yangerkun <yangerkun@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/memory-failure.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 034607a68ccb..3da3c63dccd1 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1387,7 +1387,12 @@ int memory_failure(unsigned long pfn, int flags)
return 0;
}

- if (!PageTransTail(p) && !PageLRU(p))
+ /*
+ * __munlock_pagevec may clear a writeback page's LRU flag without
+ * page_lock. We need wait writeback completion for this page or it
+ * may trigger vfs BUG while evict inode.
+ */
+ if (!PageTransTail(p) && !PageLRU(p) && !PageWriteback(p))
goto identify_page_state;

/*
--
2.30.2
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