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 DD578431A5C; Sat, 12 Sep 2026 19:10:44 +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=1789240246; cv=none; b=JYHZC8ddbPy7S0s6VB31LVIkzdiaeYwCgOFtj8/xInVvr946RKu1s+X7LC9JffKDxJdWff5Z+Ri6Woxet3Ps9Q6b8rSma02AUtoLSXTcccUQjwpEyNa/r7ahRDEIZeyALyfUdqi98O6YGy8EZ1z1ksEbD1xa7Qia9xr03mh4MIE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789240246; c=relaxed/simple; bh=hLQqB+QY3RYl7ZIzhM6p0WdO3Mbwit3tKlOjOWuW1qg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=f6yOSJ9juVBTqFWJvObjm9aXMt1JWBjb2Ka3Vhx+2j4rzGTpuWl4g5dY5E53nosNCyAC7Cnyuc60XlvHMLLd7h/YSd6XG9VirdxddfFwy7iy6K3r9bb5wPQzWlJ43y6qiV9lVQc9dAS/MudZcYPieYPZJSrCqVG6IhIx7ce3DuA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WttHyJ4e; 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="WttHyJ4e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 986161F000FF; Sat, 12 Sep 2026 19:10:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789240244; bh=2pz2PCYU+VWDT2/Sy9db2JspWQJlzRzoqzb8nklh5Y0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WttHyJ4eG6cTT7U/KItbESjfdCoSST0it2dzrFCtOm649Gvb/AFPPmZq98RUAvrdF kNzbPmeFkQkUeg59HkrDg+j7wQVZkVYrpr71QJZuIJX4G0tU0HtsssM2FIVmmfdbAx GHNXWzFVaMq7ayODwwdWKSxmdNyrkhDAiSUNj3WY= 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 5.15 830/935] perf dso: Guard against cache underflow on short reads in dso_cache__memcpy() Date: Sat, 12 Sep 2026 09:04:20 +0200 Message-ID: <20260912065545.861751440@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065526.833703348@linuxfoundation.org> References: <20260912065526.833703348@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 5.15-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 dc48f3441650a..f1005a2c28721 100644 --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -860,7 +860,20 @@ 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