From: Eric Biggers <ebiggers@kernel.org>
To: linux-xfs@vger.kernel.org
Cc: linux-ext4@vger.kernel.org, syzkaller-bugs@googlegroups.com,
linux-kernel@vger.kernel.org
Subject: [PATCH] xfs: clear PF_MEMALLOC before exiting xfsaild thread
Date: Sat, 7 Mar 2020 20:35:40 -0800 [thread overview]
Message-ID: <20200308043540.1034779-1-ebiggers@kernel.org> (raw)
In-Reply-To: <0000000000000e7156059f751d7b@google.com>
From: Eric Biggers <ebiggers@google.com>
Leaving PF_MEMALLOC set when exiting a kthread causes it to remain set
during do_exit(). That can confuse things. For example, if BSD process
accounting is enabled, then it's possible for do_exit() to end up
calling ext4_write_inode(). That triggers the
WARN_ON_ONCE(current->flags & PF_MEMALLOC) there, as it assumes
(appropriately) that inodes aren't written when allocating memory.
This case was reported by syzbot at
https://lkml.kernel.org/r/0000000000000e7156059f751d7b@google.com.
Fix this in xfsaild() by using the helper functions to save and restore
PF_MEMALLOC.
Reported-by: syzbot+1f9dc49e8de2582d90c2@syzkaller.appspotmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/xfs/xfs_trans_ail.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 00cc5b8734be..3bc570c90ad9 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -529,8 +529,9 @@ xfsaild(
{
struct xfs_ail *ailp = data;
long tout = 0; /* milliseconds */
+ unsigned int noreclaim_flag;
- current->flags |= PF_MEMALLOC;
+ noreclaim_flag = memalloc_noreclaim_save();
set_freezable();
while (1) {
@@ -601,6 +602,7 @@ xfsaild(
tout = xfsaild_push(ailp);
}
+ memalloc_noreclaim_restore(noreclaim_flag);
return 0;
}
--
2.25.1
next prev parent reply other threads:[~2020-03-08 4:36 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 6:57 WARNING in ext4_write_inode syzbot
2020-03-08 4:35 ` Eric Biggers [this message]
2020-03-08 23:03 ` [PATCH] xfs: clear PF_MEMALLOC before exiting xfsaild thread Dave Chinner
2020-03-09 1:04 ` Eric Biggers
2020-03-09 4:34 ` [PATCH v2] " Eric Biggers
2020-03-09 10:57 ` Brian Foster
2020-03-09 16:24 ` Darrick J. Wong
2020-03-09 18:04 ` Eric Biggers
2020-03-09 18:13 ` Darrick J. Wong
2020-03-09 18:57 ` [PATCH v3] " Eric Biggers
2020-03-10 15:47 ` Darrick J. Wong
2020-03-11 6:34 ` Christoph Hellwig
2020-03-12 22:20 ` [PATCH v2] " Eric Biggers
2020-03-08 4:36 ` [PATCH] cifs: clear PF_MEMALLOC before exiting demultiplex thread Eric Biggers
2020-03-08 6:16 ` [PATCH v2] " Eric Biggers
2020-03-08 18:43 ` Steve French
2020-03-09 5:56 ` Eric Biggers
2020-03-09 5:58 ` [PATCH v3] " Eric Biggers
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