* [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()
@ 2018-03-13 19:50 Salvatore Mesoraca
2018-03-14 15:42 ` David Sterba
0 siblings, 1 reply; 3+ messages in thread
From: Salvatore Mesoraca @ 2018-03-13 19:50 UTC (permalink / raw)
To: linux-kernel
Cc: kernel-hardening, linux-btrfs, Chris Mason, David Sterba,
Josef Bacik, Kees Cook, Salvatore Mesoraca
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@gmail.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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()
2018-03-13 19:50 [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum() Salvatore Mesoraca
@ 2018-03-14 15:42 ` David Sterba
2018-03-14 16:17 ` Salvatore Mesoraca
0 siblings, 1 reply; 3+ messages in thread
From: David Sterba @ 2018-03-14 15:42 UTC (permalink / raw)
To: Salvatore Mesoraca
Cc: linux-kernel, kernel-hardening, linux-btrfs, Chris Mason,
David Sterba, Josef Bacik, Kees Cook
On Tue, Mar 13, 2018 at 08:50:22PM +0100, Salvatore Mesoraca wrote:
> 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@gmail.com>
We already have a patch for that from a few days ago, but thanks anyway.
https://patchwork.kernel.org/patch/10277901/
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()
2018-03-14 15:42 ` David Sterba
@ 2018-03-14 16:17 ` Salvatore Mesoraca
0 siblings, 0 replies; 3+ messages in thread
From: Salvatore Mesoraca @ 2018-03-14 16:17 UTC (permalink / raw)
To: dsterba, Salvatore Mesoraca, linux-kernel, Kernel Hardening,
linux-btrfs, Chris Mason, David Sterba, Josef Bacik, Kees Cook
2018-03-14 16:42 GMT+01:00 David Sterba <dsterba@suse.cz>:
> We already have a patch for that from a few days ago, but thanks anyway.
>
> https://patchwork.kernel.org/patch/10277901/
Oh.. OK
Best regards,
Salvatore
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-03-14 16:17 UTC | newest]
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2018-03-13 19:50 [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum() Salvatore Mesoraca
2018-03-14 15:42 ` David Sterba
2018-03-14 16:17 ` Salvatore Mesoraca
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