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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>,
        Ronnie Sahlberg <lsahlber@redhat.com>,
        Steve French <stfrench@microsoft.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 205/218] cifs: potential buffer overflow in handling symlinks
Date:   Mon, 18 Apr 2022 14:14:31 +0200
Message-Id: <20220418121207.810235827@linuxfoundation.org>
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From: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>

[ Upstream commit 64c4a37ac04eeb43c42d272f6e6c8c12bfcf4304 ]

Smatch printed a warning:
	arch/x86/crypto/poly1305_glue.c:198 poly1305_update_arch() error:
	__memcpy() 'dctx->buf' too small (16 vs u32max)

It's caused because Smatch marks 'link_len' as untrusted since it comes
from sscanf(). Add a check to ensure that 'link_len' is not larger than
the size of the 'link_str' buffer.

Fixes: c69c1b6eaea1 ("cifs: implement CIFSParseMFSymlink()")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/link.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 38d26cbcad07..0c49e2aa7ea4 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -119,6 +119,9 @@ parse_mf_symlink(const u8 *buf, unsigned int buf_len, unsigned int *_link_len,
 	if (rc != 1)
 		return -EINVAL;
 
+	if (link_len > CIFS_MF_SYMLINK_LINK_MAXLEN)
+		return -EINVAL;
+
 	rc = symlink_hash(link_len, link_str, md5_hash);
 	if (rc) {
 		cifs_dbg(FYI, "%s: MD5 hash failure: %d\n", __func__, rc);
-- 
2.35.1