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fserve: Fix a buffer read overrun in _fs_client_access

Browse Source 
https://bugs.freedesktop.org/show_bug.cgi?id=83224

Found by clang's Address Sanitizer

	crac.num_auths = set_font_authorizations(&authorizations, &authlen,
						 client);
	/* Work around bug in xfs versions up through modular release 1.0.8
	   which rejects CreateAC packets with num_auths = 0 & authlen < 4 */
	if (crac.num_auths == 0) {
	    authorizations = padding;
	    authlen = 4;
	} else {
	    authlen = (authlen + 3) & ~0x3;
	}
	crac.length = (sizeof (fsCreateACReq) + authlen) >> 2;
	crac.acid = cur->acid;
	_fs_add_req_log(conn, FS_CreateAC);
	_fs_write(conn, (char *) &crac, sizeof (fsCreateACReq));
	_fs_write(conn, authorizations, authlen);

In the case in the report, set_font_authorizations setup authorizations as a
34 byte buffer (and authlen set to 34 as one would expect). The following
block changed authlen to 36 to make it 4byte aligned and the final _fs_write()
caused us to read 36 bytes from this 34 byte buffer.

This changes the incorrect size increase to instead use _fs_write_pad which
takes care of the padding for us.

Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>
This commit is contained in:
Jeremy Huddleston Sequoia
2016-05-30 00:46:21 -07:00
parent d967caa988
commit 6972ea08ee
1 changed files with 1 additions and 3 deletions
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4
src/fc/fserve.c
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@@ -2856,14 +2856,12 @@ _fs_client_access (FSFpePtr conn, pointer client, Bool sync)
if (crac.num_auths == 0) {
authorizations = padding;
authlen = 4;
} else {
authlen = (authlen + 3) & ~0x3;
}
crac.length = (sizeof (fsCreateACReq) + authlen) >> 2;
crac.acid = cur->acid;
_fs_add_req_log(conn, FS_CreateAC);
_fs_write(conn, (char *) &crac, sizeof (fsCreateACReq));
_fs_write(conn, authorizations, authlen);
_fs_write_pad(conn, authorizations, authlen);
/* ignore reply; we don't even care about it */
conn->curacid = 0;
cur->auth_generation = client_auth_generation(client);