From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>,
[email protected],
Alexander Viro <[email protected]>,
linux-fsdevel <[email protected]>
Cc: Palash Oswal <[email protected]>,
Sudip Mukherjee <[email protected]>,
[email protected],
[email protected],
[email protected]
Subject: [PATCH v3 2/2] io_uring: reexpand under-reexpanded iters
Date: Mon, 23 Aug 2021 11:18:45 +0100 [thread overview]
Message-ID: <4b5fcd229bbf1b73414cb77a4a0224498ebd19c9.1629713020.git.asml.silence@gmail.com> (raw)
In-Reply-To: <[email protected]>
[ 74.211232] BUG: KASAN: stack-out-of-bounds in iov_iter_revert+0x809/0x900
[ 74.212778] Read of size 8 at addr ffff888025dc78b8 by task
syz-executor.0/828
[ 74.214756] CPU: 0 PID: 828 Comm: syz-executor.0 Not tainted
5.14.0-rc3-next-20210730 #1
[ 74.216525] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 74.219033] Call Trace:
[ 74.219683] dump_stack_lvl+0x8b/0xb3
[ 74.220706] print_address_description.constprop.0+0x1f/0x140
[ 74.224226] kasan_report.cold+0x7f/0x11b
[ 74.226085] iov_iter_revert+0x809/0x900
[ 74.227960] io_write+0x57d/0xe40
[ 74.232647] io_issue_sqe+0x4da/0x6a80
[ 74.242578] __io_queue_sqe+0x1ac/0xe60
[ 74.245358] io_submit_sqes+0x3f6e/0x76a0
[ 74.248207] __do_sys_io_uring_enter+0x90c/0x1a20
[ 74.257167] do_syscall_64+0x3b/0x90
[ 74.257984] entry_SYSCALL_64_after_hwframe+0x44/0xae
old_size = iov_iter_count();
...
iov_iter_revert(old_size - iov_iter_count());
If iov_iter_revert() is done base on the initial size as above, and the
iter is truncated and not reexpanded in the middle, it miscalculates
borders causing problems. This trace is due to no one reexpanding after
generic_write_checks().
Now iters store how many bytes has been truncated, so reexpand them to
the initial state right before reverting.
Cc: [email protected]
Reported-by: Palash Oswal <[email protected]>
Reported-by: Sudip Mukherjee <[email protected]>
Reported-and-tested-by: [email protected]
Signed-off-by: Pavel Begunkov <[email protected]>
---
fs/io_uring.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a2e20a6fbfed..b225aff6d586 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3323,6 +3323,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
if (req->flags & REQ_F_NOWAIT)
goto done;
/* some cases will consume bytes even on error returns */
+ iov_iter_reexpand(iter, iter->count + iter->truncated);
iov_iter_revert(iter, io_size - iov_iter_count(iter));
ret = 0;
} else if (ret == -EIOCBQUEUED) {
@@ -3462,6 +3463,7 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
} else {
copy_iov:
/* some cases will consume bytes even on error returns */
+ iov_iter_reexpand(iter, iter->count + iter->truncated);
iov_iter_revert(iter, io_size - iov_iter_count(iter));
ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
return ret ?: -EAGAIN;
--
2.32.0
next prev parent reply other threads:[~2021-08-23 10:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 10:18 [PATCH v3 0/2] iter revert problems Pavel Begunkov
2021-08-23 10:18 ` [PATCH v3 1/2] iov_iter: track truncated size Pavel Begunkov
2021-08-23 10:18 ` Pavel Begunkov [this message]
2021-08-23 16:14 ` [PATCH v3 0/2] iter revert problems Jens Axboe
2021-09-03 20:55 ` Jens Axboe
2021-09-03 21:55 ` Al Viro
2021-09-04 0:57 ` Jens Axboe
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