On Tue, Oct 30, 2012 at 02:40:04PM -0400, Behan Webster wrote:
> From: Mark Charlebois <charlebm@xxxxxxxxx>
>
> The use of variable length arrays in structs (VLAIS) in the Linux Kernel code
> precludes the use of compilers which don't implement VLAIS (for instance the
> Clang compiler). Since ctx is always a 32-bit CRC, hard coding a size of 4
> bytes accomplishes the same thing without the use of VLAIS. This is the same
> technique already employed in fs/ext4/ext4.h
>
> Signed-off-by: Mark Charlebois <charlebm@xxxxxxxxx>
> Signed-off-by: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx>
That's reasonable, but in order to be safe to make sure we don't
accidentally introduce a stack overrun bug at some point in the
future, we should do something like this instead
+ #define JBD_MAX_CHECKSUM_SIZE 4
.
.
.
- char ctx[crypto_shash_descsize(journal->j_chksum_driver)];
+ char ctx[JBD_MAX_CHECKSUM_SIZE];
.
.
.
+ BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
+ JBD_MAX_CHECKSUM_SIZE);
I just like being careful and paranoid; using magic numeric constants
for buffer sizes is just a scary thing to do. If you could resubmit
the patch with this change, I'd really appreciate it. Thanks!!
- Ted
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