In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
binfmt_misc: reject a flag character as the field delimiter<\/p>\n
The registration string starts with a user chosen delimiter that
\nseparates the individual fields. So that the field parsers terminate
\neven on a truncated string create_entry() pads the buffer with that
\nsame delimiter:<\/p>\n
\tmemset(buf + count, del, 8);<\/p>\n
Most fields are scanned for the delimiter with strchr()\/scanarg() and
\nhappily stop on the padding. The flags field is different: instead of
\nscanning for the delimiter check_special_flags() consumes the flag
\ncharacters ‘P’, ‘O’, ‘C’ and ‘F’ and stops at the first byte that is
\nnone of them, relying on the trailing delimiter to end the scan.<\/p>\n
If the delimiter is itself a flag character the padding no longer acts
\nas a terminator. The scan swallows all eight padding bytes and keeps
\nreading past the end of the allocation until it hits a byte that is
\nnot a flag character. For example registering<\/p>\n
\tPaPEPPxPPiP<\/p>\n
with ‘P’ as the delimiter (name “a”, type extension, magic “x”,
\ninterpreter “i”, empty flags) leaves the flag scan running off the end
\nof the buffer. The registration is rejected in the end because the
\nparser does not stop exactly at buf + count, but only after the out of
\nbounds read has already happened. With an unlucky allocation layout the
\nscan can walk into an unmapped page; under KASAN it is reported as a
\nslab out of bounds read. binfmt_misc mounts are available to
\nunprivileged users in a user namespace so the read is reachable without
\nprivileges.<\/p>\n
Reject a delimiter that is one of the flag characters up front. Such a
\nregistration was always rejected anyway, only after the out of bounds
\nread, so no valid registration string changes meaning.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
binfmt_misc: reject a flag character as the field delimiter<\/p>\n
The registration string starts with a user chosen delimiter that
\nsepar<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-8758","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/8758","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8758"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8758"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8758"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}