From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 168A947F2DD; Sat, 28 Feb 2026 17:33:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300027; cv=none; b=ZqPr5+VO8OQ63KnThwhIF/CEGEkCulQjl1jRzxzgsDn3U3pN2t/4/945ZHZr6X9uoM5Tx2ltCb1nJQAq6W+o3xVlfT+r83nSZzxexjH4Xki7iQn37gO7eIfWJ4DhwF25NVhbBu4RwfDszz9jKT3eIxQEX/edfq53Ogs6hZQ2KSk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300027; c=relaxed/simple; bh=L7r/ZydBdbS3/Kljjcw3TA4m/2thEk7br8YIHdiykkw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FHSh4TOcgEgfGu7/ZwvwjbHDCTT0BKpV0MICqtGPHolds7Ph0zaJwZqZYRMt0g1zSlBo6lvLnh0+n6b7fv2CsJyL5KmhZdm3395wxhZD1D+aqdvGx2Uv2ZGtxvTYHmiRMV5Hu+wqLnow9KJCAiXTMqLBPSEnIW22z1XK9RLiaeI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=joOAxSd+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="joOAxSd+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4BF67C19425; Sat, 28 Feb 2026 17:33:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772300027; bh=L7r/ZydBdbS3/Kljjcw3TA4m/2thEk7br8YIHdiykkw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=joOAxSd+18RFQNMSpiu+tFsoWGkhYTlr9c1QilVdhK1oI5L7ECnP7lwvVaM1YXtPV Yo6hx2wRJKm7Ly8iMfmg2Nt5XcRsJEZjSyk/0wLqAMFASBDrAkDPhg48+85H/M5OSh lZWJuF4t/TcIetS83mnQJVczu/7yZhMuVCa9Djk+XxgNYMYSyfUXW7F5T2tH1fGESf thszKNLKNbs3JRZ+0pDEHr4bOZAi1/jHITn1fXb3CJgFzqYHb7latt18cnXM5I/kwR AojUe6kXfL7f+uqYcSIh24ZvjMMomCrDeEV7zfN5fd+Oeu3RLnk5JdMhMfOhmPTW2R swsi5anE/nnWg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Deepakkumar Karn , Jan Kara , Christian Brauner , Sasha Levin Subject: [PATCH 6.19 038/844] fs/buffer: add alert in try_to_free_buffers() for folios without buffers Date: Sat, 28 Feb 2026 12:19:11 -0500 Message-ID: <20260228173244.1509663-39-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228173244.1509663-1-sashal@kernel.org> References: <20260228173244.1509663-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Deepakkumar Karn [ Upstream commit b68f91ef3b3fe82ad78c417de71b675699a8467c ] try_to_free_buffers() can be called on folios with no buffers attached when filemap_release_folio() is invoked on a folio belonging to a mapping with AS_RELEASE_ALWAYS set but no release_folio operation defined. In such cases, folio_needs_release() returns true because of the AS_RELEASE_ALWAYS flag, but the folio has no private buffer data. This causes try_to_free_buffers() to call drop_buffers() on a folio with no buffers, leading to a null pointer dereference. Adding a check in try_to_free_buffers() to return early if the folio has no buffers attached, with WARN_ON_ONCE() to alert about the misconfiguration. This provides defensive hardening. Signed-off-by: Deepakkumar Karn Link: https://patch.msgid.link/20251211131211.308021-1-dkarn@redhat.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/buffer.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/buffer.c b/fs/buffer.c index 838c0c5710229..28e4d53f17173 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2948,6 +2948,10 @@ bool try_to_free_buffers(struct folio *folio) if (folio_test_writeback(folio)) return false; + /* Misconfigured folio check */ + if (WARN_ON_ONCE(!folio_buffers(folio))) + return true; + if (mapping == NULL) { /* can this still happen? */ ret = drop_buffers(folio, &buffers_to_free); goto out; -- 2.51.0