Re: [PATCH] normal/cmdline: fix hist_lines state loss and grub calloc failure check

On 2025-11-20 15:38, Sudhakar Kuppusamy wrote:
>> On 20 Nov 2025, at 1:41 PM, Avnish Chouhan <[email protected]> 
>> wrote:
>> 
>> Adding a fix for hist_lines memory leak and state loss. In
>> current code, we overwrite hist_lines before checking the
>> allocation result. If grub_calloc fails, hist_lines becomes NULL
>> and we loose the reference to the previously allocated hist_lines.
>> With this new change. On failure, hist_lines remains pointing to
>> the old valid memory. No leak, no state corruption.
>> 
>> Along with this, adding a failure check in grub_calloc(). If
>> grub_calloc fails, (e.g., due to memory allocation failure),
>> it returns NULL. Then, passing hist_lines (which would be NULL)
>> to grub_memmove() will result in a null pointer dereference,
>> and can cause an undefined behavior.
> 
> Sorry, Avnish. I don’t understand the above commit message. Could you
> please rephrase it.
> 
> Thanks,
> Sudhakar

This commit message clearly defines the problem and the intended purpose 
of this patch!

>> 
>> Signed-off-by: Avnish Chouhan <[email protected]>
>> ---
>> grub-core/normal/cmdline.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>> 
>> diff --git a/grub-core/normal/cmdline.c b/grub-core/normal/cmdline.c
>> index 9c6d9ad..14a40a4 100644
>> --- a/grub-core/normal/cmdline.c
>> +++ b/grub-core/normal/cmdline.c
>> @@ -42,7 +42,14 @@ grub_err_t
>> grub_set_history (int newsize)
>> {
>>   grub_uint32_t **old_hist_lines = hist_lines;
>> +
>>   hist_lines = grub_calloc (newsize, sizeof (grub_uint32_t *));
>> +  if (hist_lines == NULL)
>> +    {
>> +      /* We need to restore hist_lines to avoid memory leak and state 
>> loss */
>> +      hist_lines = old_hist_lines;
>> +      return grub_errno;
>> +    }
>> 
>>   /* Copy the old lines into the new buffer.  */
>>   if (old_hist_lines)
>> --
>> 2.47.1
>> 
>> 
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