On Mon 07-11-16 12:15:41, Chandan Rajendra wrote:
> The number of 'counters' elements needed in 'struct sg' is
> super_block->s_blocksize_bits + 2. Presently we have 16 'counters'
> elements in the array. This is insufficient for block sizes >= 32k. In
> such cases the memcpy operation performed in ext4_mb_seq_groups_show()
> would cause stack memory corruption.
>
> Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index a937ac7..67e6fcb 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2287,7 +2287,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
> struct ext4_group_info *grinfo;
> struct sg {
> struct ext4_group_info info;
> - ext4_grpblk_t counters[16];
> + ext4_grpblk_t counters[16 + 2];
How about using EXT4_MAX_BLOCK_LOG_SIZE + 2? It would be somewhat clearer
what that means... Having a function returning number of buddy counters in
a group info would be even better (and a constant for maximum number of
counters) but that's an independent cleanup...
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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