On Thu, Nov 18, 2010 at 10:47:12PM +0100, Joerg Roedel wrote: > The ext4_fill_super may return with value 0 in case of an error. The > reason is that the ret variable is used to store the return value of a > called function and is not set back to an error value later on. > This issue caused a NULL pointer de-ref in vfs_kern_mount on one of my > machines when it tried to mount a partition: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 > IP: [<ffffffff8112e8dc>] vfs_kern_mount+0x7c/0x180 > PGD 218480067 PUD 225323067 PMD 0 > Oops: 0000 [#1] SMP > last sysfs file: /sys/devices/system/cpu/cpu5/cache/index2/shared_cpu_map > CPU 1 > > ... > > Process mount (pid: 3591, threadinfo ffff8802258fc000, task ffff88022586dac0) > Stack: > ffff8802258fde38 0000000000000000 ffff880225e299b0 ffff880200000001 > ffffffff81a230e0 ffff880225e2c818 ffff8802258fde88 ffffffff8112ea52 > ffff8802258fde98 0000000000000246 ffff88022586dac0 0000000000000060 > Call Trace: > [<ffffffff8112ea52>] do_kern_mount+0x52/0x130 > [<ffffffff811497ff>] do_mount+0x2bf/0x810 > [<ffffffff810face3>] ? strndup_user+0x53/0x70 > [<ffffffff81149de0>] sys_mount+0x90/0xe0 > [<ffffffff81002fdb>] system_call_fastpath+0x16/0x1b > > This patch fixes the issue by using the 'err' variable instead of 'ret' > for that function-call like it is done in for all other function-calls > in ext4_fill_super too. > If have seen this issue on 2.6.36 too, so this patch may be -stable > material as well. Lukas and I have been trying to fix this bug for a couple of days now, and he actually sent off an identical patch this morning: http://www.spinics.net/lists/linux-ext4/msg21743.html (I also sent off a similar cleanup of the ext3 counterpart.) But, thanks for pointing this out! :) --D -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
