[Devel] [PATCH rh9 v2 3/4] dm-ploop: validate file descriptors more strictly

[Konstantin Khorenko]

From: Alexander Atanasov <alexander.atanasov at virtuozzo.com>

 * Check if file is opened with O_DIRECT.
 * Check if the file is a regular file.
 * If missing read permission return EACCES instead of EBADF.
 * Add error messages.

https://jira.sw.ru/browse/PSBM-142046
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 drivers/md/dm-ploop-target.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-ploop-target.c b/drivers/md/dm-ploop-target.c
index 4b50487b7fb5..1db5055c2e39 100644
--- a/drivers/md/dm-ploop-target.c
+++ b/drivers/md/dm-ploop-target.c
@@ -185,19 +185,43 @@ static void ploop_destroy(struct ploop *ploop)
 	kfree(ploop);
 }
 
-static struct file *ploop_get_delta_file(int fd)
+static struct file *ploop_get_delta_file(struct ploop *ploop, int fd)
 {
+	struct dm_target *ti = ploop->ti;
 	struct file *file;
+	int ret;
 
 	file = fget(fd);
-	if (!file)
-		return ERR_PTR(-ENOENT);
+	if (!file) {
+		ti->error = "No image file set";
+		ret = -ENOENT;
+		goto out;
+	}
+
+	if (!S_ISREG(file_inode(file)->i_mode)) {
+		ti->error = "Image file is not a regular file";
+		ret = -EINVAL;
+		goto out_err;
+	}
+
+	if (!(file->f_flags & O_DIRECT)) {
+		ti->error = "Image file is opened in cached mode";
+		ret = -EINVAL;
+		goto out_err;
+	}
+
 	if (!(file->f_mode & FMODE_READ)) {
-		fput(file);
-		return ERR_PTR(-EBADF);
+		ti->error = "Image file is opened with READ flag missing";
+		ret = -EACCES;
+		goto out_err;
 	}
 
 	return file;
+out_err:
+	fput(file);
+out:
+	return ERR_PTR(ret);
+
 }
 ALLOW_ERROR_INJECTION(ploop_get_delta_file, ERRNO_NULL);
 
@@ -274,7 +298,7 @@ static int ploop_add_deltas_stack(struct ploop *ploop, char **argv, int argc)
 		if (kstrtos32(arg, 10, &delta_fd) < 0)
 			goto out;
 
-		file = ploop_get_delta_file(delta_fd);
+		file = ploop_get_delta_file(ploop, delta_fd);
 		if (IS_ERR(file)) {
 			ret = PTR_ERR(file);
 			goto out;
-- 
2.31.1