Re: [lustre-devel] [PATCH] staging: lustre: mdc: fix NULL pointer dereference in mdc_adjust_dirpages

[Dilger, Andreas]

On Aug 22, 2016, at 10:57, James Simmons <jsimmons@xxxxxxxxxxxxx> wrote:
> 
> The function mdc_adjust_dirpages is only called on platforms which
> don't have pages 4K in size which is why kbuild only reported this
> for platforms like the Alpha. The problem was a typo in ordering of
> variables in the beginning of a while loop. We were accessing the
> dp pointer before it was kmapped.
> 
> Signed-off-by: James Simmons <jsimmons@xxxxxxxxxxxxx>

Reviewed-by: Andreas Dilger <andreas.dilger@xxxxxxxxx>

> ---
> drivers/staging/lustre/lustre/mdc/mdc_request.c |    2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/mdc/mdc_request.c b/drivers/staging/lustre/lustre/mdc/mdc_request.c
> index 88848d8..7a182be 100644
> --- a/drivers/staging/lustre/lustre/mdc/mdc_request.c
> +++ b/drivers/staging/lustre/lustre/mdc/mdc_request.c
> @@ -1133,9 +1133,9 @@ static void mdc_adjust_dirpages(struct page **pages, int cfs_pgs, int lu_pgs)
> 	int i;
> 
> 	for (i = 0; i < cfs_pgs; i++) {
> +		struct lu_dirpage *dp = kmap(pages[i]);
> 		__u64 hash_end = le64_to_cpu(dp->ldp_hash_end);
> 		__u32 flags = le32_to_cpu(dp->ldp_flags);
> -		struct lu_dirpage *dp = kmap(pages[i]);
> 		struct lu_dirpage *first = dp;
> 		struct lu_dirent *end_dirent = NULL;
> 		struct lu_dirent *ent;
> -- 
> 1.7.1
> 
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