From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f71.google.com (mail-ot1-f71.google.com [209.85.210.71]) (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 0FD321F0991 for ; Sat, 17 Jan 2026 02:32:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768617145; cv=none; b=hv49S9AFjY9kQiXL+rQGXc7JtqDQp8SoDJs6B3zNjBHVOJFXvL3gUEZWnaqLp626APnaV7uIQhQQqgB9eqf1tzFkuAqKaf5pSwS72hlpg4NYYI2NRVfcQKiaB72eOiL6qrTIqJGiyn5PHWptP+SS00S87MajZdvfBfJiFUftfnw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768617145; c=relaxed/simple; bh=Ej/9CBNRssPmpKhJQwCJl2M3Wk3Ga2rfh8WZawEcdsw=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=ZQVq86vbM2RFv0TRuRgIM8lJ6r+YfjMjYMJ6PR5lyIpdsyW5/m+1eL6HMXTYoQocL36hyrYXBcE50b4uMWZGqalkg2v4VVnpZscyl6RNZJbsBP53W2d3n4oV8xGMDstlPZJmQZsFqOEb4RMLjKvgwdrbscuwgHNZRkge3/sqPmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.210.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-ot1-f71.google.com with SMTP id 46e09a7af769-7cfd1080f66so1016342a34.2 for ; Fri, 16 Jan 2026 18:32:23 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768617143; x=1769221943; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=iA6bAcqx5EmaO97qRZ7KR3MWQnqMdS5TAf041mzEjvY=; b=sfUyUwEdJqCfuo04MmnsIaGiv1+kRDVsmHuIEC0QtLEF10rg/inZtIh1y8+oOnPWa/ KvHGf3M3Cyw8MsAyB+7usUxBS5RNzCVtpzdKT/omySgZtnI6UvkyAcvJUErTLzbi8U2c bkBcEoMN1xkiE/aQ3tPkV3HKWsoV3UG614x1sXf8KYajZjoaotPFBcGIlJpbYwhMCyxr XZbElExc6+b/u4Z/JczA3i5rtMOjJYkFyQHoP3pZH4sVpOLI2jWH9nQY3VL8e1J/VpcV GwT+BXVdICYSIhbL/dUMDa7if4lI2WN27SjtvbQ0TofW10I6rooXoBHbKucFgXNcxFtA s8HA== X-Gm-Message-State: AOJu0Yxst6JGGVdEUMgfzWFWU2py190pQjDcowAt9VOAiCG38p+6+BoX UMUJba67aKq5lmvj7UA1BgpUznn8ADUSc3ansX8qHO0iXgJAVdE3VW/BStvFDwDV/gKA0oWyDLU 7YS3ull4Tt/YqfQ56OWxuuOHW4naM5iSwYWEzB+/62mlO/L0KdL9bq+gWfEQ= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:4687:b0:65d:e1a:a8f6 with SMTP id 006d021491bc7-6611797e820mr1896507eaf.25.1768617142917; Fri, 16 Jan 2026 18:32:22 -0800 (PST) Date: Fri, 16 Jan 2026 18:32:22 -0800 In-Reply-To: <696aa7da.a70a0220.31956c.001a.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <696af4b6.050a0220.3390f1.0001.GAE@google.com> Subject: Forwarded: [PATCH] hpfs: add buffer bounds validation in hpfs_bplus_lookup From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH] hpfs: add buffer bounds validation in hpfs_bplus_lookup Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master When traversing the B+ tree in a corrupted HPFS filesystem, the btree pointer obtained from GET_BTREE_PTR() may point outside the mapped buffer's bounds if the on-disk data structures are malformed. This leads to a use-after-free when accessing btree->u.external[i] as the memory may have been freed and reallocated. Additionally, a corrupted n_used_nodes value can cause out-of-bounds array access when iterating through btree->u.internal[] or btree->u.external[] arrays. Add validation to ensure: 1. The btree pointer stays within the mapped buffer boundaries 2. The n_used_nodes value is within reasonable limits This prevents KASAN-detected use-after-free when processing malicious HPFS filesystem images. Reported-by: syzbot+8debf4b3f7c7391cd8eb@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=8debf4b3f7c7391cd8eb Signed-off-by: Deepanshu Kartikey --- fs/hpfs/anode.c | XX insertions(+), X deletions(-) diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c index XXXXXXX..YYYYYYY 100644 --- a/fs/hpfs/anode.c +++ b/fs/hpfs/anode.c @@ -XX,6 +XX,16 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode, brelse(bh); if (!(anode = hpfs_map_anode(s --- fs/hpfs/anode.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 71 insertions(+), 3 deletions(-) diff --git a/fs/hpfs/anode.c b/fs/hpfs/anode.c index a4f5321eafae..826e2142223b 100644 --- a/fs/hpfs/anode.c +++ b/fs/hpfs/anode.c @@ -19,25 +19,87 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode, struct anode *anode; int i; int c1, c2 = 0; + + printk(KERN_DEBUG "hpfs_bplus_lookup: ENTRY btree=%px bh=%px sec=%u\n", + btree, bh, sec); + go_down: if (hpfs_sb(s)->sb_chk) if (hpfs_stop_cycles(s, a, &c1, &c2, "hpfs_bplus_lookup")) return -1; + + printk(KERN_DEBUG "hpfs_bplus_lookup: go_down - btree=%px bh=%px internal=%d n_used_nodes=%u\n", + btree, bh, bp_internal(btree), btree->n_used_nodes); + if (bp_internal(btree)) { - for (i = 0; i < btree->n_used_nodes; i++) + printk(KERN_DEBUG "hpfs_bplus_lookup: Processing INTERNAL node\n"); + for (i = 0; i < btree->n_used_nodes; i++) { + printk(KERN_DEBUG "hpfs_bplus_lookup: internal[%d] file_secno=%u looking_for=%u\n", + i, le32_to_cpu(btree->u.internal[i].file_secno), sec); + if (le32_to_cpu(btree->u.internal[i].file_secno) > sec) { a = le32_to_cpu(btree->u.internal[i].down); + + printk(KERN_DEBUG "hpfs_bplus_lookup: Found match, going down to anode=%08x\n", a); + printk(KERN_DEBUG "hpfs_bplus_lookup: BEFORE brelse - bh=%px btree=%px\n", bh, btree); + brelse(bh); - if (!(anode = hpfs_map_anode(s, a, &bh))) return -1; + + printk(KERN_DEBUG "hpfs_bplus_lookup: AFTER brelse - calling hpfs_map_anode\n"); + + if (!(anode = hpfs_map_anode(s, a, &bh))) { + printk(KERN_ERR "hpfs_bplus_lookup: hpfs_map_anode FAILED for anode=%08x\n", a); + return -1; + } + + printk(KERN_DEBUG "hpfs_bplus_lookup: hpfs_map_anode SUCCESS - new_bh=%px anode=%px\n", bh, anode); + btree = GET_BTREE_PTR(&anode->btree); + /* Validate btree pointer is within buffer bounds */ + if ((unsigned long)btree < (unsigned long)bh->b_data || + (unsigned long)btree + sizeof(*btree) > (unsigned long)bh->b_data + bh->b_size) { + printk(KERN_ERR "hpfs_bplus_lookup: INVALID btree pointer! btree=%px buf_start=%px buf_end=%px\n", + btree, bh->b_data, (void *)((unsigned long)bh->b_data + bh->b_size)); + brelse(bh); + return -1; + } + + /* Validate n_used_nodes is reasonable */ + if (btree->n_used_nodes > 100) { /* Adjust based on actual max */ + printk(KERN_ERR "hpfs_bplus_lookup: SUSPICIOUS n_used_nodes=%u (too large)\n", + btree->n_used_nodes); + brelse(bh); + return -1; + } + printk(KERN_DEBUG "hpfs_bplus_lookup: NEW btree=%px (from anode->btree)\n", btree); + goto go_down; } + } hpfs_error(s, "sector %08x not found in internal anode %08x", sec, a); brelse(bh); return -1; } - for (i = 0; i < btree->n_used_nodes; i++) + + printk(KERN_DEBUG "hpfs_bplus_lookup: Processing EXTERNAL node - btree=%px bh=%px n_used_nodes=%u\n", + btree, bh, btree->n_used_nodes); + + /* Add bounds checking */ + printk(KERN_DEBUG "hpfs_bplus_lookup: Buffer bounds - bh->b_data=%px size=%zu btree=%px\n", + bh->b_data, bh->b_size, btree); + + for (i = 0; i < btree->n_used_nodes; i++) { + printk(KERN_DEBUG "hpfs_bplus_lookup: external[%d] - accessing btree->u.external[%d] at %px\n", + i, i, &btree->u.external[i]); + + /* This is line 38 - the crash point */ + printk(KERN_DEBUG "hpfs_bplus_lookup: external[%d] - reading file_secno from %px\n", + i, &btree->u.external[i].file_secno); + if (le32_to_cpu(btree->u.external[i].file_secno) <= sec && le32_to_cpu(btree->u.external[i].file_secno) + le32_to_cpu(btree->u.external[i].length) > sec) { a = le32_to_cpu(btree->u.external[i].disk_secno) + sec - le32_to_cpu(btree->u.external[i].file_secno); + + printk(KERN_DEBUG "hpfs_bplus_lookup: FOUND external match - disk_secno=%u\n", a); + if (hpfs_sb(s)->sb_chk) if (hpfs_chk_sectors(s, a, 1, "data")) { brelse(bh); return -1; @@ -49,10 +111,16 @@ secno hpfs_bplus_lookup(struct super_block *s, struct inode *inode, hpfs_inode->i_n_secs = le32_to_cpu(btree->u.external[i].length); } brelse(bh); + + printk(KERN_DEBUG "hpfs_bplus_lookup: EXIT SUCCESS - returning %u\n", a); return a; } + } + hpfs_error(s, "sector %08x not found in external anode %08x", sec, a); brelse(bh); + + printk(KERN_DEBUG "hpfs_bplus_lookup: EXIT FAILURE\n"); return -1; } -- 2.43.0