5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arnaldo Carvalho de Melo [ Upstream commit 390a9461cd73bdd13acc0f6d763618ae1ff8fa17 ] dso_cache__memcpy() computes cache_offset = offset - cache->offset, then cache_size = min(cache->size - cache_offset, size). The RB tree lookup in __dso_cache__find() matches using the full DSO__DATA_CACHE_SIZE window, but cache->size reflects the actual pread return value from dso_cache__populate(). A short pread (e.g. near end-of-file) makes cache->size smaller than DSO__DATA_CACHE_SIZE. If a subsequent access targets an offset past cache->offset + cache->size but within the DSO__DATA_CACHE_SIZE window, the cache entry is found but cache_offset exceeds cache->size. Since both are u64, the subtraction cache->size - cache_offset wraps to a large value, min() selects the caller's size, and memcpy reads out of bounds. Return 0 for an offset past the valid cached data. For a regular file a short pread only happens at end-of-file, so 0 is what a direct pread() at that offset would return: cached_io() stops its read loop as on EOF. Re-reading from the backing file would not help — a second pread at the same offset returns the same short count. Fixes: 366df72657e0 ("perf dso: Refactor dso_cache__read()") Reported-by: sashiko-bot Reviewed-by: Ian Rogers Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Namhyung Kim Signed-off-by: Sasha Levin --- tools/perf/util/dso.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c index e07c48422cd2b..caea710ffb7f8 100644 --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -853,7 +853,20 @@ static ssize_t dso_cache__memcpy(struct dso_cache *cache, u64 offset, u8 *data, u64 size, bool out) { u64 cache_offset = offset - cache->offset; - u64 cache_size = min(cache->size - cache_offset, size); + u64 cache_size; + + /* + * The RB tree matches using DSO__DATA_CACHE_SIZE, but a short + * pread may leave cache->size smaller. For a regular file a + * short pread only happens at end-of-file, so an offset past + * the valid data is EOF: return 0, matching what a direct + * pread() at that offset would return, and cached_io() then + * stops its read loop. + */ + if (cache_offset >= cache->size) + return 0; + + cache_size = min(cache->size - cache_offset, size); if (out) memcpy(data, cache->data + cache_offset, cache_size); -- 2.53.0