6.14-stable review patch. If anyone has any objections, please let me know.
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From: Lizhi Xu lizhi.xu@windriver.com
[ Upstream commit f5c84eff634ba003326aa034c414e2a9dcb7c6a7 ]
Some file systems do not support read_iter/write_iter, such as selinuxfs in this issue. So before calling them, first confirm that the interface is supported and then call it.
It is releavant in that vfs_iter_read/write have the check, and removal of their used caused szybot to be able to hit this issue.
Fixes: f2fed441c69b ("loop: stop using vfs_iter__{read,write} for buffered I/O") Reported-by: syzbot+6af973a3b8dfd2faefdc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6af973a3b8dfd2faefdc Signed-off-by: Lizhi Xu lizhi.xu@windriver.com Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/20250428143626.3318717-1-lizhi.xu@windriver.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/loop.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 61ce7ccde3445..b378d2aa49f06 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -504,6 +504,17 @@ static void loop_assign_backing_file(struct loop_device *lo, struct file *file) lo->old_gfp_mask & ~(__GFP_IO | __GFP_FS)); }
+static int loop_check_backing_file(struct file *file) +{ + if (!file->f_op->read_iter) + return -EINVAL; + + if ((file->f_mode & FMODE_WRITE) && !file->f_op->write_iter) + return -EINVAL; + + return 0; +} + /* * loop_change_fd switched the backing store of a loopback device to * a new file. This is useful for operating system installers to free up @@ -525,6 +536,10 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev, if (!file) return -EBADF;
+ error = loop_check_backing_file(file); + if (error) + return error; + /* suppress uevents while reconfiguring the device */ dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
@@ -956,6 +971,14 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
if (!file) return -EBADF; + + if ((mode & BLK_OPEN_WRITE) && !file->f_op->write_iter) + return -EINVAL; + + error = loop_check_backing_file(file); + if (error) + return error; + is_loop = is_loop_device(file);
/* This is safe, since we have a reference from open(). */