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

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> 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?

Yes, it look like crash doesn't have a description of the prohibited gdb
commands, that would be kind to users.

Anyway, I've merged this first. (with editing the commit message a bit)
https://github.com/crash-utility/crash/commit/f30c5075de1b2600240d3613f78f0ab5c495a7f2

Thanks,
Kazu