[Crash-utility] [PATCH] Do not pass through the 'sy' command to GDB

[lijiang]

在 2021年03月23日 14:11, HAGIO KAZUHITO(萩尾　一仁) 写道:
> Hi Lianbo,
> 
> -----Original Message-----
>> The 'sy' command may be misused, which is mistakenly considered as
>> the 'symbol-file' command in the crash utility, this will discard
>> symbol table from the current symbol file, and eventually caused the
>> failure of crash utility after executing the 'sys' command as below:
>>
>> crash> sy
>> GNU_GET_DATATYPE[sy]: returned via gdb_error_hook
>> Discard symbol table from `/usr/lib/debug/usr/lib/modules/5.11.0-2.el9.x86_64/vmlinux'? (y or n) Please
>> answer y or n.
>> Discard symbol table from `/usr/lib/debug/usr/lib/modules/5.11.0-2.el9.x86_64/vmlinux'? (y or n) No symbol
>> file now.
>> crash> sys
>> GNU_GET_SYMBOL_TYPE: returned via gdb_error_hook
>> double free or corruption (!prev)
>> Aborted (core dumped)
>>
>> Actually, the 'symbol-file' command has been added to the gdb-prohibited
>> list. To prevent current error, let's add the 'sy' command to the list
>> so that the crash utility does not pass the 'sy' command directly to GDB.
>>
>> Signed-off-by: Lianbo Jiang <lijiang at redhat.com>
> 
> ok, thanks.
> 
> Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> 
Thank you for the comment, Kazu.

> I'm afraid that this kind of patch work can be endless, as gdb accepts
> abbreviations of its commands.  but this is the first one I see and
> likely to hit it accidentally, I ack this patch.
> 
Agree with you. It can not cover all cases that users intentionally input
the 'wrong' commands, but it could be necessary to prevent the critical
error by the accidental input.

> However, if similar issues are reported, it would be good to think about
> a better way. (e.g. prefix matching?  I'm not sure if it's feasible and
> they're worth taking efforts to fix..)
> 
The command name abbreviations are useful in the GDB, but for the crash-utility,
need to carefully cope with this feature.

It could not be worth covering all cases about this issue as we mentioned above.
So far, I haven't found a good way to fix these problems. Maybe we could provide
a document to clarify such issues?

Thanks.
Lianbo

> Thanks,
> Kazu
> 
>> ---
>>  gdb_interface.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gdb_interface.c b/gdb_interface.c
>> index f4f4dd3993db..1f10006a2d63 100644
>> --- a/gdb_interface.c
>> +++ b/gdb_interface.c
>> @@ -702,7 +702,7 @@ static char *prohibited_list[] = {
>>  	"clear", "disable", "enable", "condition", "ignore", "frame",
>>  	"select-frame", "f", "up", "down", "catch", "tcatch", "return",
>>  	"file", "exec-file", "core-file", "symbol-file", "load", "si", "ni",
>> -	"shell",
>> +	"shell", "sy",
>>  	NULL  /* must be last */
>>  };
>>
>> --
>> 2.29.2
>