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 DA193431A4C; Tue, 11 Aug 2026 17:12:26 +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=1786468348; cv=none; b=LNYFhkweozzkJIk1gkBuJ8XpzTiqTvv+4xUaoN+jRkxTjJY7sZNKXQwx1LnVjBgGTpsCVq46L16BJbX1M2qn01O6zd9oD59QKLuw9ErAkSHeJc38iQpJwuVP5WgSSYU1fY9GsWzY1veiEDHgUTcVakYyevPKEBzdx77OYHyhHos= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786468348; c=relaxed/simple; bh=nRAE/J1F4RjeaIp94T6DfvFbqHH9zBfwF3h8QR0oGfs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N43fPPaZHkirh1Ec8tmj6efq+qwKtFpqk6LMb24LKecpoxASuJC5XOLWevkedIlmwiLAOnforGJiylaYQiCLfNwDWDMiF/uQV03qk50YPEyqUq+31ZJRMtvkSYdXCPkdg5NVgv4HOIZbD6SYbbV4NjwEnNb/KwySoOb/vENTut0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mluJTESM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mluJTESM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56D5D1F000E9; Tue, 11 Aug 2026 17:12:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786468346; bh=edC2gXtMicewaQ3Uim/RZ0IU6TrcKLdQqTeAwo9ObVE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mluJTESMT0KIFk7TF4VwtVvbrTVXckNkxFdyjG+8PmntKbQM8EYBYXVcmP8tHuEea kRY0pMLSP+dfkinTvCRgdRa9FzyCzE15J+1XXXubCm4MiRihwwAW+D9z9NIRtlpHgV sxm/36MLvW0p2zmPC/AkAaZdukayE9Kzn7ET8Vp5hQspdXT9hVfoPpK9Ei2qIPkOi5 hTLs6ZvWtQ2oFmSAGvlVyuKkOyR3ptanjahkXxxzwkui3/jWaJBqWU3svMIo46MpUx PT5MkwhQ0fsD4cjCSc4mu0eC6COQRHFcKCZ6XcEbBi9Hb7DCcWdtN7rD5Vg/KxGb5l wzxGphUWO6hjA== From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Ingo Molnar , Thomas Gleixner , James Clark , Jiri Olsa , Ian Rogers , Adrian Hunter , Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Arnaldo Carvalho de Melo , sashiko-bot Subject: [PATCH 4/5] perf dso: Guard against cache underflow on short reads in dso_cache__memcpy() Date: Tue, 11 Aug 2026 14:11:59 -0300 Message-ID: <20260811171200.30096-5-acme@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260811171200.30096-1-acme@kernel.org> References: <20260811171200.30096-1-acme@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Arnaldo Carvalho de Melo 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 (cache miss) when cache_offset falls outside the valid cached range, so the caller re-reads from the backing file. Fixes: 366df72657e0 ("perf dso: Refactor dso_cache__read()") Reported-by: sashiko-bot Cc: Adrian Hunter Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/dso.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c index 845a384a4d56779b..2cf9f44a87903d7d 100644 --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -1005,7 +1005,17 @@ 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. Treat an offset past + * the valid data as a cache miss so the caller re-reads. + */ + 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); -- 2.55.0