On (25/01/30 09:08), Dan Carpenter wrote:
> Commit 7ec2cb65ef0d ("zram: unlock slot during recompression") from
> Jan 27, 2025 (linux-next), leads to the following Smatch static
> checker warning:
>
> drivers/block/zram/zram_drv.c:1960 recompress_slot()
> warn: passing freed memory 'zstrm' (line 1943)
>
Hi Dan,
Thank you for the report.
[..]
> 1923 for (; prio < prio_max; prio++) {
> 1924 if (!zram->comps[prio])
> 1925 continue;
> 1926
> 1927 num_recomps++;
> 1928 zstrm = zcomp_stream_get(zram->comps[prio]);
> 1929 src = kmap_local_page(page);
> 1930 ret = zcomp_compress(zram->comps[prio], zstrm,
> 1931 src, &comp_len_new);
> 1932 kunmap_local(src);
> 1933
> 1934 if (ret)
> 1935 break;
> 1936
> 1937 class_index_new = zs_lookup_class_index(zram->mem_pool,
> 1938 comp_len_new);
> 1939
> 1940 /* Continue until we make progress */
> 1941 if (class_index_new >= class_index_old ||
> 1942 (threshold && comp_len_new >= threshold)) {
> 1943 zcomp_stream_put(zram->comps[prio], zstrm);
>
> Imagine we hit this continue path. The right thing is probably to set
> zstrm = NULL before the continue or it might be to set ret = -EINVAL.
We still need to make sure that ZRAM_INCOMPRESSIBLE is set appropriately,
so zstrm = NULL won't do the trick. Let me take a look.
