From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C6F2A2DC794 for ; Fri, 14 Nov 2025 19:37:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763149068; cv=none; b=C2j6rqbPadcve3GWx/GYMZFujvrh8djodVRl9Jc0uvGBg+pkkk8YOhMZCqGCDI0bITBWnp69/lAJNsfNr3Jq9+251mwrka8D+orxdUQoaXAKdrFNkfIU93BLDpkaXaDI6u5LEsMdAB3DmUzHxeTAJPbK8rShCuP+78//Z1ozRcg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763149068; c=relaxed/simple; bh=w8x1vgY5Ytuh+8oAzT9I6DYuO6E1SOohSBxub76r0Qc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=mQEkY2s7wkXAb3PzIRYmFrZUVJkqzOVmMfnXhcsypEwEbEBNucArZ2UPursiY8aSbUwGH8r3jDiGO2B6d0JIokqy7RALK3Tv7SkKO3EWAEGzlRgafTBjn1R1fmXhwEj5ahNZ/TI4ptDH9/6As34EXKI8bw6KkblS74eUQuJlsvs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=ee.vjti.ac.in; spf=none smtp.mailfrom=ee.vjti.ac.in; dkim=pass (1024-bit key) header.d=vjti.ac.in header.i=@vjti.ac.in header.b=Uij6YR61; arc=none smtp.client-ip=209.85.210.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=ee.vjti.ac.in Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ee.vjti.ac.in Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=vjti.ac.in header.i=@vjti.ac.in header.b="Uij6YR61" Received: by mail-pf1-f181.google.com with SMTP id d2e1a72fcca58-7aad4823079so2162595b3a.0 for ; Fri, 14 Nov 2025 11:37:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vjti.ac.in; s=google; t=1763149065; x=1763753865; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=XU8vU/KjPE99lkBMAKIxdrPamg7+p9OoEjvmjp1kXQ0=; b=Uij6YR61Shp5ZP4jQszTu+cOvK3TIsJcqyGL/WyjtUGgKSW2yfrt1evIDNUiRDaQao TEjjWxwoaRkW4aM1Z99VsIu0nBfp/FHl/L2ioW6r6esQaiGTZsJg7SmMvFSldcD9A/iT +mcIeTOiy1OZNFBEdiMbBlsfnfw1reZfhW2Tw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763149065; x=1763753865; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=XU8vU/KjPE99lkBMAKIxdrPamg7+p9OoEjvmjp1kXQ0=; b=rGgExLhw8l4SWKrw70AbsW3r+qg5k1dHEicBoFqHGQc+qeJc/LCaQYYyaRTYGEeCDQ 2tSP9MqYXChfDaY9g4d+7CkgvVMDaYCGeSZr+QGi0e+3BGlx4XWAUd88HYqitwyGUgnw 9CL8ZAqd/+tHYgqs4hJ3MrrEn8R3rYtJMqOMqYpGuViFDcM6qH2/sqI/jt8UFNbYHFfp 5RXfS2y2RMlNWThnfejZgauLUFXMkd2Llc/6e/VcpQIFRRpkA0oPKjs1GDjvlHq4nERY 53C5KqllMKva+I1r2RdAG21CTTNqx6Ez03+sqe96tJRp4NaTnJqW5k7aNQo/GuK+b3Pr FQeA== X-Forwarded-Encrypted: i=1; AJvYcCU5Cn7TVXcsUwMBJW7Mwcy1cbLrZQRY68DpEvuoecssJuu42tYfuHbZKlm4wBAcP2rWvVYpIpTspRc0Etk5MP73zFKOgA==@lists.linux.dev X-Gm-Message-State: AOJu0YwA7WpKReHduUYwWe+40D4QOAXOS0y4dTz6UQEk9LEH65Y6/qUl FTb1kquCfZ4XsV98oK2JezayWKWR3ql4C/VplKo2BVs1uTaTy+h+JOgp3m3T7bpr4g4= X-Gm-Gg: ASbGncvFa6yFS3iMu+KDRAkRGr8C2sIBVJx7ePzjYXQZ9i/Qe97AliS7EchaQAWqd14 to9OgTSe3FH12hnRWAPHcWdsFAJl2SYcDM3ftldPNRVIP9LqhGkyms322JIn/e6L+YgxA40FxwQ bPuVPfjBrm342UpSlzGB357DtJI7Vebdjh6+ifauWUbcIA9MAlPb3MPeJFRxHfhhbLjUVtEaUXk CuOhCknwjeTBI6sGjjoyl2txPG/k2mVNUfuPa4rMBVVvlZvOqoMQ6eurp3Uxzd6cNRL5W4jQkXd tMVaSVHNzkzgssVmfAA+2xePrAZfwz8pq53z2Pb8T5jxsslPZjeBGbKsiRwmE/YobPXejeOpMSP BUHwv+G+PaeXl6kG2vWnY1xdKvh+7a8HkRWfF60OSw7HaMFIsBteKcsDVkiHlcgvfjivYdNaMQI gTCx5vH/4rR9TuE+BBvzRBHOwOLrzQsfbR/zHGw8BNrDkZeqN5OYQs9b19 X-Google-Smtp-Source: AGHT+IE+LbpWEktarCB2Dnrv1yWZrNsnZpDCOeAp7apnz9uVsWtNi+RAN9rwFssQKUSctcc6Q3Qc9w== X-Received: by 2002:a05:6a00:2e8f:b0:7b9:7349:4f0f with SMTP id d2e1a72fcca58-7ba3799f055mr4742484b3a.0.1763149064968; Fri, 14 Nov 2025 11:37:44 -0800 (PST) Received: from ranegod-HP-ENVY-x360-Convertible-13-bd0xxx.. ([2405:201:31:d869:6873:3448:fe16:68a6]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7b9250cd5f6sm5941807b3a.16.2025.11.14.11.37.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Nov 2025 11:37:44 -0800 (PST) From: ssrane_b23@ee.vjti.ac.in X-Google-Original-From: ssranevjti@gmail.com To: willy@infradead.org Cc: akpm@linux-foundation.org, shakeel.butt@linux.dev, eddyz87@gmail.com, andrii@kernel.org, ast@kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, khalid@kernel.org, Shaurya Rane , syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com Subject: [PATCH] mm/filemap: fix NULL pointer dereference in do_read_cache_folio() Date: Sat, 15 Nov 2025 01:07:29 +0530 Message-Id: <20251114193729.251892-1-ssranevjti@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Shaurya Rane When read_cache_folio() is called with a NULL filler function on a mapping that does not implement read_folio, a NULL pointer dereference occurs in filemap_read_folio(). The crash occurs when: build_id_parse() is called on a VMA backed by a file from a filesystem that does not implement ->read_folio() (e.g. procfs, sysfs, or other virtual filesystems). read_cache_folio() is called with filler = NULL. do_read_cache_folio() assigns filler = mapping->a_ops->read_folio, which is still NULL. filemap_read_folio() calls filler(), causing a NULL pointer dereference. The fix is to add a NULL check after the fallback assignment and return -EIO. Callers handle this error safely. Reported-by: syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d Fixes: ad41251c290d ("lib/buildid: implement sleepable build_id_parse() API") Signed-off-by: Shaurya Rane --- mm/filemap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 13f0259d993c..f700fe931d61 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3980,6 +3980,8 @@ static struct folio *do_read_cache_folio(struct address_space *mapping, if (!filler) filler = mapping->a_ops->read_folio; + if (!filler) + return ERR_PTR(-EIO); repeat: folio = filemap_get_folio(mapping, index); if (IS_ERR(folio)) { -- 2.34.1