[Crash-utility] Re: [Crash-Utility][PATCH] symbols.c: skip non-exist module memory type

On 2024/04/02 16:29, Tao Liu wrote: > Hi Naveen, > > On Tue, Apr 2, 2024 at 3:17 PM Naveen Chaudhary > <naveenchaudhary2010(a)hotmail.com&gt; 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(a)redhat.com&gt; >> Sent: Tuesday, April 2, 2024 12:15 PM >> To: devel(a)lists.crash-utility.osci.io <devel(a)lists.crash-utility.osci.io&gt; >> Cc: Tao Liu <ltao(a)redhat.com>; Naveen Chaudhary <naveenchaudhary2010(a)hotmail.com&gt; >> 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] >> $8 = (struct syment *) 0x4dcbb48 >> >> mod_mem MOD_RO_AFTER_INIT(3) and MOD_INIT_RODATA(6) is not exist, which should >> be skipped, otherwise a segfault will happen. >> >> Fixes: 7750e61fdb2a ("Support module memory layout change on Linux 6.4") >> >> Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; >> Reported-by: Naveen Chaudhary <naveenchaudhary2010(a)hotmail.com&gt; >> --- >> symbols.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/symbols.c b/symbols.c >> index cbc9ed1..27e55c6 100644 >> --- a/symbols.c >> +++ b/symbols.c >> @@ -5580,7 +5580,7 @@ value_search_module_6_4(ulong value, ulong *offset) >> sp = lm->symtable[t]; >> sp_end = lm->symend[t]; >> >> - if (value < sp->value || value > sp_end->value) >> + if (!sp || value < sp->value || value > sp_end->value) >> continue; >> >> splast = NULL; >> -- >> 2.40.1 >> > -- > Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io > To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io > https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ > Contribution Guidelines: https://github.com/crash-utility/crash/wiki