Re: [PATCH 3/4] xfs_logprint: fix some unaligned accesses

Eric Sandeen
2015-10-09T13:48:10Z

On 10/9/15 8:24 AM, Brian Foster wrote:
> On Thu, Oct 08, 2015 at 07:25:50PM -0500, Eric Sandeen wrote:
>> This routine had a fair bit of gyration to avoid unaligned accesses,
>> but didn't fix them all. Fix some more spotted at runtime by libubsan.
>>
>> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
>> ---
>> logprint/log_misc.c | 18 +++++++++++++++---
>> repair/btree.c | 1 +
>> 2 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/logprint/log_misc.c b/logprint/log_misc.c
>> index d76145c..6cd249a 100644
>> --- a/logprint/log_misc.c
>> +++ b/logprint/log_misc.c
>> @@ -325,7 +325,11 @@ xlog_print_trans_buffer(char **ptr, int len, int *i, int num_ops)
>> }
>> super_block = 0;
>> } else if (be32_to_cpu(*(__be32 *)(*ptr)) == XFS_AGI_MAGIC) {
>> - agi = (xfs_agi_t *)(*ptr);
>> + struct xfs_agi agi_s;
>> +
>> + /* memmove because *ptr may not be 8-byte aligned */
>> + memmove(&agi_s, *ptr, sizeof(struct xfs_agi));
>> + agi = &agi_s;
>
> Nit: could we either define the new variables in the same scope as the
> pointer (either here or at the top of the function), or just ditch the
> pointers altogether?

Let me see how that looks, sure.

>> printf(_("AGI Buffer: XAGI "));
>> /*
>> * v4 filesystems only contain the fields before the uuid.
> ...
>> diff --git a/repair/btree.c b/repair/btree.c
>> index 66fb40b..e31e67a 100644
>> --- a/repair/btree.c
>> +++ b/repair/btree.c
>> @@ -230,6 +230,7 @@ btree_get_next(
>> }
>> if (level == 0) {
>> if (key) {
>> + /* XXXX what if index past MAX? What if no next? */
>
> Unintentional hunk?

Yeah, dammit, I thought I removed that, sorry.

Thanks,
-Eric