linux-kernel - [PATCH] efs: removed useless conditional checks in function

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Date:   Thu,  7 Jul 2022 17:26:52 +0300
From:   Andrey Strachuk <strochuk@...ras.ru>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     Andrey Strachuk <strochuk@...ras.ru>, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org
Subject: [PATCH] efs: removed useless conditional checks in function

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@...ras.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