[PATCH AUTOSEL 4.19 180/237] ocfs2: don't use iocb when EIOCBQUEUED returns

Sasha Levin
2019-11-16T15:46:42Z

From: Changwei Ge <ge.changwei@h3c.com>

[ Upstream commit 9e985787750db8aae87f02b67e908f28ac4d6b83 ]

When -EIOCBQUEUED returns, it means that aio_complete() will be called
from dio_complete(), which is an asynchronous progress against
write_iter. Generally, IO is a very slow progress than executing
instruction, but we still can't take the risk to access a freed iocb.

And we do face a BUG crash issue. Using the crash tool, iocb is
obviously freed already.

crash> struct -x kiocb ffff881a350f5900
struct kiocb {
ki_filp = 0xffff881a350f5a80,
ki_pos = 0x0,
ki_complete = 0x0,
private = 0x0,
ki_flags = 0x0
}

And the backtrace shows:
ocfs2_file_write_iter+0xcaa/0xd00 [ocfs2]
aio_run_iocb+0x229/0x2f0
do_io_submit+0x291/0x540
SyS_io_submit+0x10/0x20
system_call_fastpath+0x16/0x75

Link: http://lkml.kernel.org/r/1523361653-14439-1-git-send-email-ge.changwei@h3c.com
Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.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>
---
fs/ocfs2/file.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index a847fe52c56ee..a3e077fcfeb9b 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2389,7 +2389,7 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,

written = __generic_file_write_iter(iocb, from);
/* buffered aio wouldn't have proper lock coverage today */
- BUG_ON(written == -EIOCBQUEUED && !(iocb->ki_flags & IOCB_DIRECT));
+ BUG_ON(written == -EIOCBQUEUED && !direct_io);

/*
* deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
@@ -2509,7 +2509,7 @@ static ssize_t ocfs2_file_read_iter(struct kiocb *iocb,
trace_generic_file_read_iter_ret(ret);

/* buffered aio wouldn't have proper lock coverage today */
- BUG_ON(ret == -EIOCBQUEUED && !(iocb->ki_flags & IOCB_DIRECT));
+ BUG_ON(ret == -EIOCBQUEUED && !direct_io);

/* see ocfs2_file_write_iter */
if (ret == -EIOCBQUEUED || !ocfs2_iocb_is_rw_locked(iocb)) {
--
2.20.1