From: Greg Kroah-Hartman Date: Mon, 6 Apr 2026 13:49:37 +0000 (+0200) Subject: smb: client: fix off-by-8 bounds check in check_wsl_eas() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3d8b9d06bd3ac4c6846f5498800b0f5f8062e53b;p=thirdparty%2Fkernel%2Flinux.git smb: client: fix off-by-8 bounds check in check_wsl_eas() The bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA name and value, but ea_data sits at offset sizeof(struct smb2_file_full_ea_info) = 8 from ea, not at offset 0. The strncmp() later reads ea->ea_data[0..nlen-1] and the value bytes follow at ea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1 + vlen. Isn't pointer math fun? The earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the 8-byte header is in bounds, but since the last EA is placed within 8 bytes of the end of the response, the name and value bytes are read past the end of iov. Fix this mess all up by using ea->ea_data as the base for the bounds check. An "untrusted" server can use this to leak up to 8 bytes of kernel heap into the EA name comparison and influence which WSL xattr the data is interpreted as. Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: stable Assisted-by: gregkh_clanker_t1000 Reviewed-by: Paulo Alcantara (Red Hat) Signed-off-by: Greg Kroah-Hartman Signed-off-by: Steve French --- diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c index 364bdcff9c9d5..fe1c9d7765806 100644 --- a/fs/smb/client/smb2inode.c +++ b/fs/smb/client/smb2inode.c @@ -128,7 +128,7 @@ static int check_wsl_eas(struct kvec *rsp_iov) nlen = ea->ea_name_length; vlen = le16_to_cpu(ea->ea_value_length); if (nlen != SMB2_WSL_XATTR_NAME_LEN || - (u8 *)ea + nlen + 1 + vlen > end) + (u8 *)ea->ea_data + nlen + 1 + vlen > end) return -EINVAL; switch (vlen) {