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author | Eric W. Biederman <ebiederm@xmission.com> | 2020-05-29 22:00:54 -0500 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2020-05-29 22:00:54 -0500 |
commit | 56305aa9b6fab91a5555a45796b79c1b0a6353d1 (patch) | |
tree | 378ea4452668d448b0834fd08008a5f81619f1fd /security/selinux | |
parent | a7868323c2638a7c6c5b30b37831b73cbdf0dc15 (diff) | |
download | linux-56305aa9b6fab91a5555a45796b79c1b0a6353d1.tar.gz linux-56305aa9b6fab91a5555a45796b79c1b0a6353d1.tar.bz2 linux-56305aa9b6fab91a5555a45796b79c1b0a6353d1.zip |
exec: Compute file based creds only once
Move the computation of creds from prepare_binfmt into begin_new_exec
so that the creds need only be computed once. This is just code
reorganization no semantic changes of any kind are made.
Moving the computation is safe. I have looked through the kernel and
verified none of the binfmts look at bprm->cred directly, and that
there are no helpers that look at bprm->cred indirectly. Which means
that it is not a problem to compute the bprm->cred later in the
execution flow as it is not used until it becomes current->cred.
A new function bprm_creds_from_file is added to contain the work that
needs to be done. bprm_creds_from_file first computes which file
bprm->executable or most likely bprm->file that the bprm->creds
will be computed from.
The funciton bprm_fill_uid is updated to receive the file instead of
accessing bprm->file. The now unnecessary work needed to reset the
bprm->cred->euid, and bprm->cred->egid is removed from brpm_fill_uid.
A small comment to document that bprm_fill_uid now only deals with the
work to handle suid and sgid files. The default case is already
heandled by prepare_exec_creds.
The function security_bprm_repopulate_creds is renamed
security_bprm_creds_from_file and now is explicitly passed the file
from which to compute the creds. The documentation of the
bprm_creds_from_file security hook is updated to explain when the hook
is called and what it needs to do. The file is passed from
cap_bprm_creds_from_file into get_file_caps so that the caps are
computed for the appropriate file. The now unnecessary work in
cap_bprm_creds_from_file to reset the ambient capabilites has been
removed. A small comment to document that the work of
cap_bprm_creds_from_file is to read capabilities from the files
secureity attribute and derive capabilities from the fact the
user had uid 0 has been added.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'security/selinux')
0 files changed, 0 insertions, 0 deletions