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capabilities: add a securebit to disable PR_CAP_AMBIENT_RAISE

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Per Andrew Morgan's request, add a securebit to allow admins to disable
PR_CAP_AMBIENT_RAISE.  This securebit will prevent processes from adding
capabilities to their ambient set.

For simplicity, this disables PR_CAP_AMBIENT_RAISE entirely rather than
just disabling setting previously cleared bits.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Aaron Jones <aaronmdjones@gmail.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Andrew G. Morgan <morgan@kernel.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: Markku Savela <msa@moth.iki.fi>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Lutomirski 2015-09-04 15:42:51 -07:00 committed by Linus Torvalds
parent 32ae976ed3
commit 746bf6d642
2 changed files with 12 additions and 2 deletions
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11
include/uapi/linux/securebits.h
View File

@ -43,9 +43,18 @@
#define SECBIT_KEEP_CAPS (issecure_mask(SECURE_KEEP_CAPS))
#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
/* When set, a process cannot add new capabilities to its ambient set. */
#define SECURE_NO_CAP_AMBIENT_RAISE 6
#define SECURE_NO_CAP_AMBIENT_RAISE_LOCKED 7 /* make bit-6 immutable */
#define SECBIT_NO_CAP_AMBIENT_RAISE (issecure_mask(SECURE_NO_CAP_AMBIENT_RAISE))
#define SECBIT_NO_CAP_AMBIENT_RAISE_LOCKED \
(issecure_mask(SECURE_NO_CAP_AMBIENT_RAISE_LOCKED))
#define SECURE_ALL_BITS (issecure_mask(SECURE_NOROOT) | \
issecure_mask(SECURE_NO_SETUID_FIXUP) | \
issecure_mask(SECURE_KEEP_CAPS))
issecure_mask(SECURE_KEEP_CAPS) | \
issecure_mask(SECURE_NO_CAP_AMBIENT_RAISE))
#define SECURE_ALL_LOCKS (SECURE_ALL_BITS << 1)
#endif /* _UAPI_LINUX_SECUREBITS_H */

3
security/commoncap.c
View File

@ -993,7 +993,8 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
if (arg2 == PR_CAP_AMBIENT_RAISE &&
(!cap_raised(current_cred()->cap_permitted, arg3) ||
!cap_raised(current_cred()->cap_inheritable,
arg3)))
arg3) ||
issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
return -EPERM;
new = prepare_creds();