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exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds

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Today security_bprm_set_creds has several implementations:
apparmor_bprm_set_creds, cap_bprm_set_creds, selinux_bprm_set_creds,
smack_bprm_set_creds, and tomoyo_bprm_set_creds.

Except for cap_bprm_set_creds they all test bprm->called_set_creds and
return immediately if it is true.  The function cap_bprm_set_creds
ignores bprm->calld_sed_creds entirely.

Create a new LSM hook security_bprm_creds_for_exec that is called just
before prepare_binprm in __do_execve_file, resulting in a LSM hook
that is called exactly once for the entire of exec.  Modify the bits
of security_bprm_set_creds that only want to be called once per exec
into security_bprm_creds_for_exec, leaving only cap_bprm_set_creds
behind.

Remove bprm->called_set_creds all of it's former users have been moved
to security_bprm_creds_for_exec.

Add or upate comments a appropriate to bring them up to date and
to reflect this change.

Link: https://lkml.kernel.org/r/87v9kszrzh.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com> # For the LSM and Smack bits
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman
2020-03-22 15:46:24 -05:00
parent 87b047d2be
commit b8bff59926
12 changed files with 63 additions and 63 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/binfmts.h
View File

@@ -27,22 +27,14 @@ struct linux_binprm {
unsigned long argmin; /* rlimit marker for copy_strings() */
unsigned int
/*
* True after the bprm_set_creds hook has been called once
* (multiple calls can be made via prepare_binprm() for
* binfmt_script/misc).
*/
called_set_creds:1,
/*
* True if most recent call to the commoncaps bprm_set_creds
* hook (due to multiple prepare_binprm() calls from the
* binfmt_script/misc handlers) resulted in elevated
* privileges.
* True if most recent call to cap_bprm_set_creds
* resulted in elevated privileges.
*/
cap_elevated:1,
/*
* Set by bprm_set_creds hook to indicate a privilege-gaining
* exec has happened. Used to sanitize execution environment
* and to set AT_SECURE auxv for glibc.
* Set by bprm_creds_for_exec hook to indicate a
* privilege-gaining exec has happened. Used to set
* AT_SECURE auxv for glibc.
*/
secureexec:1,
/*