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 8D8811875 for ; Wed, 28 Dec 2022 15:57:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14370C433EF; Wed, 28 Dec 2022 15:57:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672243050; bh=aQFaecaqcH30nHzpU+8RbcjuDn2x7otmuRN7p6ZP31U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D6pwrAH9FbqCDjWoflf2CYkD0Czs2hC0LxPwVYDyR//BLljRS6EWQ8GPQ5yR8I1dq 7pYCa+zU1MXYsqaFprSn2rSx9JZIpHetRgFoOI1LBeF3PAuw84dZAy2RsRYdKMNfHQ GqJX9Q+kPU6U+EexB6aKEfNYEaRi3HhfRPP/n8eU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com, Hawkins Jiawei , Mike Kravetz , Muchun Song , Ian Kent , Andrew Morton , Sasha Levin Subject: [PATCH 5.15 678/731] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param() Date: Wed, 28 Dec 2022 15:43:05 +0100 Message-Id: <20221228144316.128020522@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20221228144256.536395940@linuxfoundation.org> References: <20221228144256.536395940@linuxfoundation.org> User-Agent: quilt/0.67 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 From: Hawkins Jiawei [ Upstream commit 26215b7ee923b9251f7bb12c4e5f09dc465d35f2 ] Syzkaller reports a null-ptr-deref bug as follows: ====================================================== KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380 [...] Call Trace: vfs_parse_fs_param fs/fs_context.c:148 [inline] vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129 vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231 do_new_mount fs/namespace.c:3036 [inline] path_mount+0x12de/0x1e20 fs/namespace.c:3370 do_mount fs/namespace.c:3383 [inline] __do_sys_mount fs/namespace.c:3591 [inline] __se_sys_mount fs/namespace.c:3568 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] ====================================================== According to commit "vfs: parse: deal with zero length string value", kernel will set the param->string to null pointer in vfs_parse_fs_string() if fs string has zero length. Yet the problem is that, hugetlbfs_parse_param() will dereference the param->string, without checking whether it is a null pointer. To be more specific, if hugetlbfs_parse_param() parses an illegal mount parameter, such as "size=,", kernel will constructs struct fs_parameter with null pointer in vfs_parse_fs_string(), then passes this struct fs_parameter to hugetlbfs_parse_param(), which triggers the above null-ptr-deref bug. This patch solves it by adding sanity check on param->string in hugetlbfs_parse_param(). Link: https://lkml.kernel.org/r/20221020231609.4810-1-yin31149@gmail.com Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/ Signed-off-by: Hawkins Jiawei Reviewed-by: Mike Kravetz Cc: Hawkins Jiawei Cc: Muchun Song Cc: Ian Kent Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- fs/hugetlbfs/inode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index be8deec29ebe..352230a011e0 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1250,7 +1250,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par case Opt_size: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->max_size_opt = memparse(param->string, &rest); ctx->max_val_type = SIZE_STD; @@ -1260,7 +1260,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par case Opt_nr_inodes: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->nr_inodes = memparse(param->string, &rest); return 0; @@ -1276,7 +1276,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par case Opt_min_size: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->min_size_opt = memparse(param->string, &rest); ctx->min_val_type = SIZE_STD; -- 2.35.1