| Message ID | 20200831182353.14593-1-cai@lca.pw (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | [v4] iomap: fix WARN_ON_ONCE() from unprivileged users | expand |
On Mon, Aug 31, 2020 at 02:23:53PM -0400, Qian Cai wrote: > 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> Looks good, Reviewed-by: Christoph Hellwig <hch@lst.de>
On Mon, Aug 31, 2020 at 02:23:53PM -0400, Qian Cai wrote: > 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> Looks ok to me too. Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> --D > --- > 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 >
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;
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(+)