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authorDavid Howells <dhowells@redhat.com>2008-11-14 10:39:19 +1100
committerJames Morris <jmorris@namei.org>2008-11-14 10:39:19 +1100
commitc69e8d9c01db2adc503464993c358901c9af9de4 (patch)
treebed94aaa9aeb7a7834d1c880f72b62a11a752c78 /kernel/ptrace.c
parent86a264abe542cfececb4df129bc45a0338d8cdb9 (diff)
downloadlinux-2.6.34-ux500-c69e8d9c01db2adc503464993c358901c9af9de4.tar.gz
CRED: Use RCU to access another task's creds and to release a task's own creds
Use RCU to access another task's creds and to release a task's own creds. This means that it will be possible for the credentials of a task to be replaced without another task (a) requiring a full lock to read them, and (b) seeing deallocated memory. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'kernel/ptrace.c')
-rw-r--r--kernel/ptrace.c22
1 files changed, 13 insertions, 9 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 49849d12dd1..b9d5f4e4f6a 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -115,7 +115,7 @@ int ptrace_check_attach(struct task_struct *child, int kill)
int __ptrace_may_access(struct task_struct *task, unsigned int mode)
{
- struct cred *cred = current->cred, *tcred = task->cred;
+ const struct cred *cred = current_cred(), *tcred;
/* May we inspect the given task?
* This check is used both for attaching with ptrace
@@ -125,19 +125,23 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
* because setting up the necessary parent/child relationship
* or halting the specified task is impossible.
*/
- uid_t uid = cred->uid;
- gid_t gid = cred->gid;
int dumpable = 0;
/* Don't let security modules deny introspection */
if (task == current)
return 0;
- if ((uid != tcred->euid ||
- uid != tcred->suid ||
- uid != tcred->uid ||
- gid != tcred->egid ||
- gid != tcred->sgid ||
- gid != tcred->gid) && !capable(CAP_SYS_PTRACE))
+ rcu_read_lock();
+ tcred = __task_cred(task);
+ if ((cred->uid != tcred->euid ||
+ cred->uid != tcred->suid ||
+ cred->uid != tcred->uid ||
+ cred->gid != tcred->egid ||
+ cred->gid != tcred->sgid ||
+ cred->gid != tcred->gid) &&
+ !capable(CAP_SYS_PTRACE)) {
+ rcu_read_unlock();
return -EPERM;
+ }
+ rcu_read_unlock();
smp_rmb();
if (task->mm)
dumpable = get_dumpable(task->mm);