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authorQian Cai <cai@lca.pw>2020-09-10 08:26:15 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2020-09-10 08:26:15 -0700
commita805c111650cdba6ee880f528abdd03c1af82089 (patch)
treefc7db90d60dccf7c13ec19455ec2fb0cc4031207 /fs/iomap
parentf4d51dffc6c01a9e94650d95ce0104964f8ae822 (diff)
iomap: fix WARN_ON_ONCE() from unprivileged users
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> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'fs/iomap')
-rw-r--r--fs/iomap/direct-io.c10
1 files changed, 10 insertions, 0 deletions
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;