From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3435A39936E; Sat, 12 Sep 2026 20:02:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789243323; cv=none; b=Q1lbX3glVQXLFvwukYPJh3uMzglKZ4FgCc5Bipm6LP7AuslWtJ5fPUUWd36Mwt60aDBAM6Wn4x+5oxHhell7DzWtzFwn/P1W3Nmkzb8SlwwUbeNhAekpTXKp9eUwkJ669tCGAB54pEHgwlDUoeGVzkbDhXjL0TsbL3Sfz6eqd6A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789243323; c=relaxed/simple; bh=MeN3VB87Pzrp/I34dm5m73V2VP4ojt/T48/a8GTrt10=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=oUxGpqCKqGP74l1c7b6iPq4w/n/tdItK1LUcSGgoVKWrh2mKy5d4i6QhpkLUBnL7idh69rMcQ63ID+CiZaTMZMxjBh4X1h+SyTi8P2bwA7H+bsBKIE/7pSBT6umTA3WjRMX4c25fAl1Db0I9gHe9rqHtUAFtosysso1p6aTCttg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EFQyoeOL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="EFQyoeOL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FEAD1F000FF; Sat, 12 Sep 2026 20:02:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789243322; bh=Hl+LEnMwBtchyfcFuUPmKRVlDQNCL+XmS0IGGFLrOO0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EFQyoeOLDYsPAiXPbipeIy3JdrAwJJtMwj1P3lC/h2W51L3q8OYS0S+HX1EGWqYST cVBz+/DtSXUbloL5hHlHcailBFPlAeqi/k5l+sRv0cPPrs3mj2Gb9cTURc6yzVrp1M JF4kQVpTzqGO0cvoz3V3Yy0b8sOZF9GYxfTiArOA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, sashiko-bot , Ian Rogers , Arnaldo Carvalho de Melo , Namhyung Kim , Sasha Levin Subject: [PATCH 5.10 715/798] perf dso: Guard against cache underflow on short reads in dso_cache__memcpy() Date: Sat, 12 Sep 2026 09:05:43 +0200 Message-ID: <20260912065533.470916645@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065516.948645775@linuxfoundation.org> References: <20260912065516.948645775@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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