linux-kernel - Re: WARNING: kmalloc bug in krealloc

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Date:   Mon, 16 Jul 2018 16:17:42 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     v9fs-developer@...ts.sourceforge.net,
        Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>
Cc:     syzbot <syzbot+8574471d8734457d98aa@...kaller.appspotmail.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: Re: WARNING: kmalloc bug in krealloc

This looks like a v9fs bug. xattrwalk is returning bogus return value.

[   30.321571] v9fs_xattr_get(): name = security.capability buffer =           (null) value_len = 0
[   30.323819] >>> TXATTRWALK file_fid 1, attr_fid 2 name security.capability
[   30.326132] <<<  RXATTRWALK fid 2 size 17441174723711270912
[   30.327667] attr_size=17441174723711270912 buffer_size=0 retval=-1005569349998280704
[   30.329684] vfs_getxattr_alloc(): value=          (null) error=5570560 xattr_size=24
[   30.331610] WARNING: CPU: 2 PID: 8807 at mm/slab_common.c:1031 kmalloc_slab+0x56/0x70

-1005569349998280704 is 0xF20B800100550000, and taking lower 32bits of F20B800100550000 is
0x550000 which is 5570560, which is too large size for kmalloc().