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Message-Id: <1520970622-19535-1-git-send-email-s.mesoraca16@gmail.com>
Date: Tue, 13 Mar 2018 20:50:22 +0100
From: Salvatore Mesoraca <s.mesoraca16@...il.com>
To: linux-kernel@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com,
linux-btrfs@...r.kernel.org,
Chris Mason <clm@...com>,
David Sterba <dsterba@...e.com>,
Josef Bacik <jbacik@...com>,
Kees Cook <keescook@...omium.org>,
Salvatore Mesoraca <s.mesoraca16@...il.com>
Subject: [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()
Avoid a VLA[1] by using a real constant expression instead of a variable.
The compiler should be able to optimize the original code and avoid using
an actual VLA. Anyway this change is useful because it will avoid a false
positive with -Wvla, it might also help the compiler generating better
code.
[1] https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
---
fs/btrfs/disk-io.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 21f34ad..88cef92 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -403,8 +403,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
u32 crc = ~(u32)0;
- const int csum_size = sizeof(crc);
- char result[csum_size];
+ char result[sizeof(crc)];
/*
* The super_block structure does not span the whole
@@ -415,7 +414,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
btrfs_csum_final(crc, result);
- if (memcmp(raw_disk_sb, result, csum_size))
+ if (memcmp(raw_disk_sb, result, sizeof(result)))
ret = 1;
}
--
1.9.1
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