Re: [PATCH v3] gdb: replace alloca with gdb::unique_xmalloc_ptr in remote-fileio.c

[Luis <luis.machado.foss@gmail.com>]

On 01/07/2026 20:08, Pedro Alves wrote:
> On 2026-07-01 20:01, Luis Machado wrote:
>> remote_fileio_extract_ptr_w_len parsed a debuggee controlled 64 bit
>> length, narrowed it to int with no bounds check, and the value flowed
>> directly into alloca() across RSP File I/O handlers (Fopen, Frename,
>> Funlink, Fstat, Fsystem).  A malicious inferior or remote stub could
>> send a crafted packet with a large path length, displacing the stack
>> pointer by up to 2 GiB and potentially crashing the debugger.
>>
>> remote_fileio_extract_ptr_w_len now rejects negative lengths, lengths
>> that would overflow the int result (greater than INT_MAX), and zero.
>> An allow_zero_length flag lets the Fsystem handler opt in to the zero
>> length sentinel that signals a NULL cmdline query.  All other handlers
>> use the default and are protected without any per call checks.  Oversized
>> names are rejected naturally by the underlying syscall with ENAMETOOLONG.
>> All alloca(length) calls have been replaced with
>> gdb::unique_xmalloc_ptr<char>, so an oversized but positive length now
>> fails as a graceful heap allocation error rather than corrupting the
>> stack.
>>
>> Add a selftest that exercises various problematic cases.
>>
>> Signed-off-by: Luis Machado <luis.machado@amd.com>
> 
> Approved-By: Pedro Alves <pedro@palves.net>
> 

Thanks. Pushed now.