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Re: [PATCH] xfs_repair: junk last entry in sf dir if name starts beyond

To: Rui Gomes <rgomes@xxxxxx>
Subject: Re: [PATCH] xfs_repair: junk last entry in sf dir if name starts beyond dir size
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Wed, 11 Mar 2015 11:46:50 -0400
Cc: omar <omar@xxxxxx>, xfs <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1908077521.428877.1426086242030.JavaMail.zimbra@xxxxxx>
References: <54FDFEDC.5090106@xxxxxxxxxxx> <1061986380.422955.1426008424991.JavaMail.zimbra@xxxxxx> <54FF2BBF.7060404@xxxxxxxxxxx> <410959445.428221.1426083973347.JavaMail.zimbra@xxxxxx> <550054D9.3010602@xxxxxxxxxxx> <1908077521.428877.1426086242030.JavaMail.zimbra@xxxxxx>
On 3/11/15 11:04 AM, Rui Gomes wrote:
> Program received signal SIGSEGV, Segmentation fault.
> 0x000000000044dbcd in __xfs_dir3_data_check (dp=dp@entry=0x0, 
> bp=bp@entry=0x1538e810) at xfs_dir2_data.c:148
> 148                             for (i = 0; i < be32_to_cpu(btp->count); i++) 
> {
> (gdb) bt
> #0  0x000000000044dbcd in __xfs_dir3_data_check (dp=dp@entry=0x0, 
> bp=bp@entry=0x1538e810) at xfs_dir2_data.c:148
> #1  0x000000000044b9ea in xfs_dir3_block_verify (bp=bp@entry=0x1538e810) at 
> xfs_dir2_block.c:62

Can you do a little digging around in gdb to sort out more
about why it segfaulted?

We got a xfs_dir2_data_hdr_t from the passed-in bp w/ valid magic:

hdr = bp->b_addr;

and from that got btp:

        switch (hdr->magic) {
        case cpu_to_be32(XFS_DIR2_BLOCK_MAGIC):
                btp = xfs_dir2_block_tail_p(mp, hdr);

and this just finds an offset from hdr:

                ((char *)hdr + mp->m_dirblksize)) - 1;

but then apparently blew up when we tried to use btp:

for (i = 0; i < be32_to_cpu(btp->count); i++) {

I don't see offhand how the hdr is ok, with good magic, but an
offset from the hdr (btp) is causing a segfault.  Can you dig around
a bit more in gdb?

-Eric

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