Eric W. Biederman 68fe063327 exec: Always set cap_ambient in cap_bprm_set_creds
[ Upstream commit a4ae32c71f ]

An invariant of cap_bprm_set_creds is that every field in the new cred
structure that cap_bprm_set_creds might set, needs to be set every
time to ensure the fields does not get a stale value.

The field cap_ambient is not set every time cap_bprm_set_creds is
called, which means that if there is a suid or sgid script with an
interpreter that has neither the suid nor the sgid bits set the
interpreter should be able to accept ambient credentials.
Unfortuantely because cap_ambient is not reset to it's original value
the interpreter can not accept ambient credentials.

Given that the ambient capability set is expected to be controlled by
the caller, I don't think this is particularly serious.  But it is
definitely worth fixing so the code works correctly.

I have tested to verify my reading of the code is correct and the
interpreter of a sgid can receive ambient capabilities with this
change and cannot receive ambient capabilities without this change.

Cc: stable@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
Fixes: 58319057b7 ("capabilities: ambient capabilities")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-06-03 08:21:23 +02:00
2020-06-03 08:21:15 +02:00
2020-05-27 17:46:53 +02:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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