From: Qian Cai <cai@lca.pw>
To: darrick.wong@oracle.com
Cc: hch@infradead.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Qian Cai <cai@lca.pw>
Subject: [PATCH v4] iomap: fix WARN_ON_ONCE() from unprivileged users
Date: Mon, 31 Aug 2020 14:23:53 -0400 [thread overview]
Message-ID: <20200831182353.14593-1-cai@lca.pw> (raw)
It is trivial to trigger a WARN_ON_ONCE(1) in iomap_dio_actor() by
unprivileged users which would taint the kernel, or worse - panic if
panic_on_warn or panic_on_taint is set. Hence, just convert it to
pr_warn_ratelimited() to let users know their workloads are racing.
Thank Dave Chinner for the initial analysis of the racing reproducers.
Signed-off-by: Qian Cai <cai@lca.pw>
---
v4: use %pD4.
v3: Keep the default case and update the message.
v2: Record the path, pid and command as well.
fs/iomap/direct-io.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index c1aafb2ab990..9519113ebc35 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -388,6 +388,16 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
case IOMAP_INLINE:
return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
+ case IOMAP_DELALLOC:
+ /*
+ * DIO is not serialised against mmap() access at all, and so
+ * if the page_mkwrite occurs between the writeback and the
+ * iomap_apply() call in the DIO path, then it will see the
+ * DELALLOC block that the page-mkwrite allocated.
+ */
+ pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
+ dio->iocb->ki_filp, current->comm);
+ return -EIO;
default:
WARN_ON_ONCE(1);
return -EIO;
--
2.18.4
next reply other threads:[~2020-08-31 18:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 18:23 Qian Cai [this message]
2020-09-01 5:21 ` [PATCH v4] iomap: fix WARN_ON_ONCE() from unprivileged users Christoph Hellwig
2020-09-01 15:12 ` Darrick J. Wong
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200831182353.14593-1-cai@lca.pw \
--to=cai@lca.pw \
--cc=darrick.wong@oracle.com \
--cc=hch@infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-xfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).