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perf maps: Avoid RC_CHK use after free

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The case of __maps__fixup_overlap_and_insert where the "new" maps
covers existing mappings can create a use-after-free with reference
count checking enabled. The issue is that "pos" holds a map pointer
from maps_by_address that is put from maps_by_address but then used to
look for a map in maps_by_name (the compared map is now a
use-after-free). The issue stems from using maps__remove which redoes
some of the searches already done by __maps__fixup_overlap_and_insert,
so optimize the code (by avoiding repeated searches) and avoid the
use-after-free by inlining the appropriate removal code.

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202511141407.f9edcfa6-lkp@intel.com
Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers 2025-11-18 21:05:54 -08:00 committed by Namhyung Kim
parent 51d87d977e
commit 245cfbcd3d
1 changed files with 20 additions and 2 deletions
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22
tools/perf/util/maps.c
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@ -931,8 +931,9 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
return err;
} else {
struct map *next = NULL;
unsigned int nr_maps = maps__nr_maps(maps);
if (i + 1 < maps__nr_maps(maps))
if (i + 1 < nr_maps)
next = maps_by_address[i + 1];
if (!next || map__start(next) >= map__end(new)) {
@ -953,7 +954,24 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
check_invariants(maps);
return err;
}
__maps__remove(maps, pos);
/*
* pos fully covers the previous mapping so remove
* it. The following is an inlined version of
* maps__remove that reuses the already computed
* indices.
*/
map__put(maps_by_address[i]);
memmove(&maps_by_address[i],
&maps_by_address[i + 1],
(nr_maps - i - 1) * sizeof(*maps_by_address));
if (maps_by_name) {
map__put(maps_by_name[ni]);
memmove(&maps_by_name[ni],
&maps_by_name[ni + 1],
(nr_maps - ni - 1) * sizeof(*maps_by_name));
}
--RC_CHK_ACCESS(maps)->nr_maps;
check_invariants(maps);
/*
* Maps are ordered but no need to increase `i` as the