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proc: don't show nonexistent capabilities 

Without this patch it is really hard to interpret a bounding set, if
CAP_LAST_CAP is unknown for a current kernel.

Non-existant capabilities can not be deleted from a bounding set with help
of prctl.

E.g.: Here are two examples without/with this patch.

  CapBnd:	ffffffe0fdecffff
  CapBnd:	00000000fdecffff

I suggest to hide non-existent capabilities. Here is two reasons.
* It's logically and easier for using.
* It helps to checkpoint-restore capabilities of tasks, because tasks
can be restored on another kernel, where CAP_LAST_CAP is bigger.

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Cc: Andrew G. Morgan <morgan@kernel.org>
Reviewed-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrew Vagin 2012-12-17 16:03:10 -08:00 committed by Linus Torvalds
parent 992fb6e170
commit 7b9a7ec565
1 changed files with 9 additions and 0 deletions
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9
fs/proc/array.c
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@ -308,6 +308,10 @@ static void render_cap_t(struct seq_file *m, const char *header,
seq_putc(m, '\n');
}
/* Remove non-existent capabilities */
#define NORM_CAPS(v) (v.cap[CAP_TO_INDEX(CAP_LAST_CAP)] &= \
CAP_TO_MASK(CAP_LAST_CAP + 1) - 1)
static inline void task_cap(struct seq_file *m, struct task_struct *p)
{
const struct cred *cred;
@ -321,6 +325,11 @@ static inline void task_cap(struct seq_file *m, struct task_struct *p)
cap_bset = cred->cap_bset;
rcu_read_unlock();
NORM_CAPS(cap_inheritable);
NORM_CAPS(cap_permitted);
NORM_CAPS(cap_effective);
NORM_CAPS(cap_bset);
render_cap_t(m, "CapInh:\t", &cap_inheritable);
render_cap_t(m, "CapPrm:\t", &cap_permitted);
render_cap_t(m, "CapEff:\t", &cap_effective);