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CRED: Use RCU to access another task's creds and to release a task's own creds

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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>
This commit is contained in:
David Howells 2008-11-14 10:39:19 +11:00 • committed by James Morris
parent 86a264abe5
commit c69e8d9c01
28 changed files with 353 additions and 202 deletions
Download patch file Download diff file Expand all files Collapse all files

32
fs/proc/array.c
View file

@ -159,6 +159,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
struct group_info *group_info;
int g;
struct fdtable *fdt = NULL;
const struct cred *cred;
pid_t ppid, tpid;
rcu_read_lock();
@ -170,6 +171,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
if (tracer)
tpid = task_pid_nr_ns(tracer, ns);
}
cred = get_cred((struct cred *) __task_cred(p));
seq_printf(m,
"State:\t%s\n"
"Tgid:\t%d\n"
@ -182,8 +184,8 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
task_tgid_nr_ns(p, ns),
pid_nr_ns(pid, ns),
ppid, tpid,
p->cred->uid, p->cred->euid, p->cred->suid, p->cred->fsuid,
p->cred->gid, p->cred->egid, p->cred->sgid, p->cred->fsgid);
cred->uid, cred->euid, cred->suid, cred->fsuid,
cred->gid, cred->egid, cred->sgid, cred->fsgid);
task_lock(p);
if (p->files)
@ -194,13 +196,12 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
fdt ? fdt->max_fds : 0);
rcu_read_unlock();
group_info = p->cred->group_info;
get_group_info(group_info);
group_info = cred->group_info;
task_unlock(p);
for (g = 0; g < min(group_info->ngroups, NGROUPS_SMALL); g++)
seq_printf(m, "%d ", GROUP_AT(group_info, g));
put_group_info(group_info);
put_cred(cred);
seq_printf(m, "\n");
}
@ -262,7 +263,7 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p)
blocked = p->blocked;
collect_sigign_sigcatch(p, &ignored, &caught);
num_threads = atomic_read(&p->signal->count);
qsize = atomic_read(&p->cred->user->sigpending);
qsize = atomic_read(&__task_cred(p)->user->sigpending);
qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur;
unlock_task_sighand(p, &flags);
}
@ -293,12 +294,21 @@ static void render_cap_t(struct seq_file *m, const char *header,
static inline void task_cap(struct seq_file *m, struct task_struct *p)
{
struct cred *cred = p->cred;
const struct cred *cred;
kernel_cap_t cap_inheritable, cap_permitted, cap_effective, cap_bset;
render_cap_t(m, "CapInh:\t", &cred->cap_inheritable);
render_cap_t(m, "CapPrm:\t", &cred->cap_permitted);
render_cap_t(m, "CapEff:\t", &cred->cap_effective);
render_cap_t(m, "CapBnd:\t", &cred->cap_bset);
rcu_read_lock();
cred = __task_cred(p);
cap_inheritable = cred->cap_inheritable;
cap_permitted = cred->cap_permitted;
cap_effective = cred->cap_effective;
cap_bset = cred->cap_bset;
rcu_read_unlock();
render_cap_t(m, "CapInh:\t", &cap_inheritable);
render_cap_t(m, "CapPrm:\t", &cap_permitted);
render_cap_t(m, "CapEff:\t", &cap_effective);
render_cap_t(m, "CapBnd:\t", &cap_bset);
}
static inline void task_context_switch_counts(struct seq_file *m,