Re: [PATCH v1 04/11] perf annotate: Smatch: Fix dereferencing freed memory

[Arnaldo Carvalho de Melo]

Em Tue, Jul 02, 2019 at 06:34:13PM +0800, Leo Yan escreveu:
> Based on the following report from Smatch, fix the potential
> dereferencing freed memory check.
> 
>   tools/perf/util/annotate.c:1125
>   disasm_line__parse() error: dereferencing freed memory 'namep'
> 
> tools/perf/util/annotate.c
> 1100 static int disasm_line__parse(char *line, const char **namep, char **rawp)
> 1101 {
> 1102         char tmp, *name = ltrim(line);
> 
> [...]
> 
> 1114         *namep = strdup(name);
> 1115
> 1116         if (*namep == NULL)
> 1117                 goto out_free_name;
> 
> [...]
> 
> 1124 out_free_name:
> 1125         free((void *)namep);
>                           ^^^^^
> 1126         *namep = NULL;
>              ^^^^^^
> 1127         return -1;
> 1128 }
> 
> If strdup() fails to allocate memory space for *namep, we don't need to
> free memory with pointer 'namep', which is resident in data structure
> disasm_line::ins::name; and *namep is NULL pointer for this failure, so
> it's pointless to assign NULL to *namep again.

Applied, with this extra comment:


Committer note:

Freeing namep, which is the address of the first entry of the 'struct
ins' that is the first member of struct disasm_line would in fact free
that disasm_line instance, if it was allocated via malloc/calloc, which,
later, would a dereference of freed memory.