On 2024/04/02 16:29, Tao Liu wrote:
> Hi Naveen,
>
> On Tue, Apr 2, 2024 at 3:17 PM Naveen Chaudhary
> <naveenchaudhary2010@xxxxxxxxxxx> wrote:
>>
>> Thanks Tao,
>>
>> On a funny side, though I didn't understand this area of code much, but I ironically made the exact same fix to avoid problem for time being on my side, thinking there might be a different fix coming 🙂. Glad its now taken care. Thanks 🙂
>>
>
> IMHO this is the right fix. If you look through the crash code, there
> are plenty of cases like:
>
> for_each_mod_mem_type(t) {
> if (!lm->symtable[t])
> continue;
>
> So it shouldn't be an exception here. Just my opinion, let's see how
> other people think of it.
Agreed, the same style sounds better.
Thank you for reporting the issue and fixing.
Thanks,
Kazu
If you want to know more about the
> background, you can check the patchset 7750e61fdb2a ("Support module
> memory layout change on Linux 6.4"), which will give you more info.
>
> In addition, please feel free to post your code, even if you are not
> very confident of it. The mailing list is open for discussion :)
>
> Thanks,
> Tao Liu
>
>> Regards,
>> Naveen
>>
>>
>> ________________________________
>> From: Tao Liu <ltao@xxxxxxxxxx>
>> Sent: Tuesday, April 2, 2024 12:15 PM
>> To: devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx <devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
>> Cc: Tao Liu <ltao@xxxxxxxxxx>; Naveen Chaudhary <naveenchaudhary2010@xxxxxxxxxxx>
>> Subject: [Crash-Utility][PATCH] symbols.c: skip non-exist module memory type
>>
>> Not all mod_mem_type will be included for kernel modules. E.g. in the
>> following module case:
>>
>> (gdb) p lm->symtable[0]
>> $1 = (struct syment *) 0x4dcbad0
>> (gdb) p lm->symtable[1]
>> $2 = (struct syment *) 0x4dcbb70
>> (gdb) p lm->symtable[2]
>> $3 = (struct syment *) 0x4dcbc10
>> (gdb) p lm->symtable[3]
>> $4 = (struct syment *) 0x0
>> (gdb) p lm->symtable[4]
>> $5 = (struct syment *) 0x4dcbcb0
>> (gdb) p lm->symtable[5]
>> $6 = (struct syment *) 0x4dcbd00
>> (gdb) p lm->symtable[6]
>> $7 = (struct syment *) 0x0
>> (gdb) p lm->symtable[7]
>> $8 = (struct syment *) 0x4dcbb48
>>
>> mod_mem MOD_RO_AFTER_INIT(3) and MOD_INIT_RODATA(6) is not exist, which should
>> be skipped, otherwise a segfault will happen.
>>
>> Fixes: 7750e61fdb2a ("Support module memory layout change on Linux 6.4")
>>
>> Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
>> Reported-by: Naveen Chaudhary <naveenchaudhary2010@xxxxxxxxxxx>
>> ---
>> symbols.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/symbols.c b/symbols.c
>> index cbc9ed1..27e55c6 100644
>> --- a/symbols.c
>> +++ b/symbols.c
>> @@ -5580,7 +5580,7 @@ value_search_module_6_4(ulong value, ulong *offset)
>> sp = lm->symtable[t];
>> sp_end = lm->symend[t];
>>
>> - if (value < sp->value || value > sp_end->value)
>> + if (!sp || value < sp->value || value > sp_end->value)
>> continue;
>>
>> splast = NULL;
>> --
>> 2.40.1
>>
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