[PATCH] efs: removed useless conditional checks in function

[PATCH] efs: removed useless conditional checks in function

[Andrey Strachuk]

At lines 300 and 305, variable "bh" is compared with NULL.

-----------------------------------------------------------
293	exts = (efs_extent *) bh->b_data;
294
295	extent_copy(&(exts[ioffset]), &ext);
296
297	if (ext.cooked.ex_magic != 0) {
298		pr_err("extent %d has bad magic number in block %d\n",
299		       cur, iblock);
300		if (bh) brelse(bh);
301		return 0;
302	}
303
304	if ((result = efs_extent_check(&ext, block, sb))) {
305		if (bh) brelse(bh);
306		in->lastextent = cur;
307		return result;
308	}
-----------------------------------------------------------

However, it cannot be NULL because kernel crashes at
line 293 otherwise.
The patch removes useless comparisons.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
---
 fs/efs/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/efs/inode.c b/fs/efs/inode.c
index 3ba94bb005a6..a88a0600cdfb 100644
--- a/fs/efs/inode.c
+++ b/fs/efs/inode.c
@@ -297,12 +297,12 @@ efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
 		if (ext.cooked.ex_magic != 0) {
 			pr_err("extent %d has bad magic number in block %d\n",
 			       cur, iblock);
-			if (bh) brelse(bh);
+			brelse(bh);
 			return 0;
 		}
 
 		if ((result = efs_extent_check(&ext, block, sb))) {
-			if (bh) brelse(bh);
+			brelse(bh);
 			in->lastextent = cur;
 			return result;
 		}
-- 
2.25.1

Re: [PATCH] efs: removed useless conditional checks in function

[Matthew Wilcox]

On Thu, Jul 07, 2022 at 05:26:52PM +0300, Andrey Strachuk wrote:
> However, it cannot be NULL because kernel crashes at
> line 293 otherwise.
> The patch removes useless comparisons.

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Not sure who's going to merge this patch.  I guess I can throw it into
the pagecache tree if nobody else wants it.

> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

If you really want to be fancy, you can delve into linux-fullhistory and
come up with:

Fixes: 2b50c6738b500 ("Import 2.3.2")

although I bet that breaks a few scripts.