[PATCH 1/2] fs: exfat: Perform NULL check before dereference

[Andrew Goodbody]

In the functions exfat_pread and exfat_pwrite there is a NULL check for
ctxt.cur_dev but this has already been derefenced twice before this
happens.
Refactor the code a bit to put the NULL check first.

This issue found by Smatch.

Signed-off-by: Andrew Goodbody <andrew.goodbody at linaro.org>
---
 fs/exfat/io.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/exfat/io.c b/fs/exfat/io.c
index 77cd2dfb6dc..d80eece6850 100644
--- a/fs/exfat/io.c
+++ b/fs/exfat/io.c
@@ -442,12 +442,15 @@ off_t exfat_get_size(const struct exfat_dev* dev)
 ssize_t exfat_pread(struct exfat_dev* dev, void* buffer, size_t size,
 		off_t offset)
 {
-	lbaint_t sect = offset >> ctxt.cur_dev->log2blksz;
-	int off = offset & (ctxt.cur_dev->blksz - 1);
+	lbaint_t sect;
+	int off;
 
 	if (!ctxt.cur_dev)
 		return -EIO;
 
+	sect = offset >> ctxt.cur_dev->log2blksz;
+	off = offset & (ctxt.cur_dev->blksz - 1);
+
 	if (fs_devread(ctxt.cur_dev, &ctxt.cur_part_info, sect,
 		       off, size, buffer))
 		return 0;
@@ -457,12 +460,15 @@ ssize_t exfat_pread(struct exfat_dev* dev, void* buffer, size_t size,
 ssize_t exfat_pwrite(struct exfat_dev* dev, const void* buffer, size_t size,
 		off_t offset)
 {
-	lbaint_t sect = offset >> ctxt.cur_dev->log2blksz;
-	int off = offset & (ctxt.cur_dev->blksz - 1);
+	lbaint_t sect;
+	int off;
 
 	if (!ctxt.cur_dev)
 		return -EIO;
 
+	sect = offset >> ctxt.cur_dev->log2blksz;
+	off = offset & (ctxt.cur_dev->blksz - 1);
+
 	if (fs_devwrite(ctxt.cur_dev, &ctxt.cur_part_info, sect,
 		       off, size, buffer))
 		return 0;

-- 
2.39.5