On 2022/12/21 14:22, HAGIO KAZUHITO(萩尾 一仁) wrote:
> On 2022/12/20 12:16, Lianbo Jiang wrote:
>> Recently the following failure has been observed on some vmcores when
>> using the mount command:
>>
>> crash> mount
>> MOUNT SUPERBLK TYPE DEVNAME DIRNAME
>> ffff97a4818a3480 ffff979500013800 rootfs none /
>> ffff97e4846ca700 ffff97e484653000 sysfs sysfs /sys
>> ...
>> ffff97b484753420 0 mount: invalid kernel virtual address: 0 type: "super_block buffer"
>
> Thank you for the fix.
>
> Just out of curiosity, do you see why the vfsmount.mnt_sb is zero?
> That panic occurred during mounting or unmounting?
I think, it might be more helpful to print the MOUNT and SUPERBLK values
in the list even if it's zero or invalid, rather than skip it completely.
What do you think? e.g. continue here:
@@ -1500,6 +1500,11 @@ show_mounts(ulong one_vfsmount, int flags, struct task_context *namespace_contex
mkstring(buf2, VADDR_PRLEN, RJUST|LONG_HEX,
MKSTR(sbp)));
+ if (!IS_KVADDR(sbp)) {
+ error(INFO, "cannot get super_block\n");
+ continue;
+ }
+
readmem(sbp, KVADDR, super_block_buf, SIZE(super_block),
"super_block buffer", FAULT_ON_ERROR);
type = ULONG(super_block_buf + OFFSET(super_block_s_type));
Thanks,
Kazu
>
> Thanks,
> Kazu
>
>>
>> The kernel virtual address of the super_block is zero when the mount
>> command fails at the address 0xffff97b484753420. And the remaining
>> dumping information will be discarded. That is not expected.
>>
>> Check the address and skip it, if this is an invalid kernel virtual
>> address, that can avoid truncating the remaining mount dumps.
>>
>> Reported-by: Dave Wysochanski <dwysocha@xxxxxxxxxx>
>> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
>> ---
>> filesys.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/filesys.c b/filesys.c
>> index c2ea78de821d..8c2d4e316208 100644
>> --- a/filesys.c
>> +++ b/filesys.c
>> @@ -1491,6 +1491,8 @@ show_mounts(ulong one_vfsmount, int flags, struct task_context *namespace_contex
>> }
>>
>> sbp = ULONG(vfsmount_buf + OFFSET(vfsmount_mnt_sb));
>> + if (!IS_KVADDR(sbp))
>> + continue;
>>
>> if (flags)
>> fprintf(fp, "%s", mount_hdr);
> --
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