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t=1671499350; bh=aJlILcbht/YEnxfR7Jkxij3uWW+rqVcQU1fJAnSJwA0=; h=From:To:Cc:Subject:Date:From; b=B/KCIjQkJ+orw0sGRBcKRPbKBxBnqCTGpCQzOL+SEwUt0LyM5rJtdIDB5pcz5eGDw yov/amRo8UZIk+oPdhAHVvk7Lsj756ThGL5zjs7PJhlkkHvM3uFum6sg/6758AXGX3 el2z2TIwbFEYFqOgJFr3UukCDVBS/8ZgNLV1FlBrREmnoGvdoW8vEhxjHpm0U/p/dz aVBnDhS1OfpDofYA5FU3VgYAMDry+Qj4s6zX9WlqsOL1Qk/ANHtV4IhwZUf82qvfru iSlCHlIAkG+Y85ZFACsAq/ifaD+dDWM8RgiGxj6C6YbBMkiSuMaCtD3CxoNTFeQhy5 Av1uF0n5AdtRA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Hawkins Jiawei , syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com, Mike Kravetz , Muchun Song , Ian Kent , Andrew Morton , Sasha Levin , muchun.song@linux.dev, linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.4 1/5] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param() Date: Mon, 19 Dec 2022 20:22:23 -0500 Message-Id: <20221220012227.1222729-1-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4A1C920005 X-Rspam-User: X-Stat-Signature: 9tww577do8pozcwnm178xwumbtj3xjeu X-HE-Tag: 1671499352-748350 X-HE-Meta: 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 GgKa79+T jFCq89GjsjPP4Pn4dFuxBUSkj6JqkYddEbr2a8DATrNJ0s2kb7xhuyfvnxwrjnUGzzXzl7HnpTWEvAs8IUQKcpjLcoKWsXmaxFz8KD67kvFSiBUu4/kTGskkSQ4BxAwUbU1D36jxNzR2jAO1YWDKgO11/pv81J1RPmWGSHXoPfQmzcRspBM+z8UrC7KMQfulo5YgaGFNh0RV/CGbLMFt80a9wgA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 7d039ba5ae28..b1d31c78fc9d 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1232,7 +1232,7 @@ 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; @@ -1242,7 +1242,7 @@ 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; @@ -1258,7 +1258,7 @@ 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