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seccomp: Switch from atomic_t to recount_t 

This switches the seccomp usage tracking from atomic_t to refcount_t to
gain refcount overflow protections.

Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: David Windsor <dwindsor@gmail.com>
Cc: Hans Liljestrand <hans.liljestrand@aalto.fi>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2017-06-26 09:24:00 -07:00
parent 93bd70e333
commit 0b5fa22906
1 changed files with 5 additions and 5 deletions
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10
kernel/seccomp.c
View File

@ -13,7 +13,7 @@
* of Berkeley Packet Filters/Linux Socket Filters. * of Berkeley Packet Filters/Linux Socket Filters.
*/ */
#include <linux/atomic.h> #include <linux/refcount.h>
#include <linux/audit.h> #include <linux/audit.h>
#include <linux/compat.h> #include <linux/compat.h>
#include <linux/coredump.h> #include <linux/coredump.h>
@ -56,7 +56,7 @@
* to a task_struct (other than @usage). * to a task_struct (other than @usage).
*/ */
struct seccomp_filter { struct seccomp_filter {
atomic_t usage; refcount_t usage;
struct seccomp_filter *prev; struct seccomp_filter *prev;
struct bpf_prog *prog; struct bpf_prog *prog;
}; };
@ -378,7 +378,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
return ERR_PTR(ret); return ERR_PTR(ret);
} }
atomic_set(&sfilter->usage, 1); refcount_set(&sfilter->usage, 1);
return sfilter; return sfilter;
} }
@ -465,7 +465,7 @@ void get_seccomp_filter(struct task_struct *tsk)
if (!orig) if (!orig)
return; return;
/* Reference count is bounded by the number of total processes. */ /* Reference count is bounded by the number of total processes. */
atomic_inc(&orig->usage); refcount_inc(&orig->usage);
} }
static inline void seccomp_filter_free(struct seccomp_filter *filter) static inline void seccomp_filter_free(struct seccomp_filter *filter)
@ -481,7 +481,7 @@ void put_seccomp_filter(struct task_struct *tsk)
{ {
struct seccomp_filter *orig = tsk->seccomp.filter; struct seccomp_filter *orig = tsk->seccomp.filter;
/* Clean up single-reference branches iteratively. */ /* Clean up single-reference branches iteratively. */
while (orig && atomic_dec_and_test(&orig->usage)) { while (orig && refcount_dec_and_test(&orig->usage)) {
struct seccomp_filter *freeme = orig; struct seccomp_filter *freeme = orig;
orig = orig->prev; orig = orig->prev;
seccomp_filter_free(freeme); seccomp_filter_free(freeme);