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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 <[email protected]>
Acked-by: James Morris <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: James Morris <[email protected]>
This commit is contained in:
David Howells 2008-11-14 10:39:19 +11:00 • committed by James Morris
commit c69e8d9c01
28 changed files with 355 additions and 204 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,

32
fs/proc/base.c
View file

@ -1406,6 +1406,7 @@ static struct inode *proc_pid_make_inode(struct super_block * sb, struct task_st
{
struct inode * inode;
struct proc_inode *ei;
const struct cred *cred;
/* We need a new inode */
@ -1428,8 +1429,11 @@ static struct inode *proc_pid_make_inode(struct super_block * sb, struct task_st
inode->i_uid = 0;
inode->i_gid = 0;
if (task_dumpable(task)) {
inode->i_uid = task->cred->euid;
inode->i_gid = task->cred->egid;
rcu_read_lock();
cred = __task_cred(task);
inode->i_uid = cred->euid;
inode->i_gid = cred->egid;
rcu_read_unlock();
}
security_task_to_inode(task, inode);
@ -1445,6 +1449,8 @@ static int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat
{
struct inode *inode = dentry->d_inode;
struct task_struct *task;
const struct cred *cred;
generic_fillattr(inode, stat);
rcu_read_lock();
@ -1454,8 +1460,9 @@ static int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat
if (task) {
if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
task_dumpable(task)) {
stat->uid = task->cred->euid;
stat->gid = task->cred->egid;
cred = __task_cred(task);
stat->uid = cred->euid;
stat->gid = cred->egid;
}
}
rcu_read_unlock();
@ -1483,11 +1490,16 @@ static int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct inode *inode = dentry->d_inode;
struct task_struct *task = get_proc_task(inode);
const struct cred *cred;
if (task) {
if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
task_dumpable(task)) {
inode->i_uid = task->cred->euid;
inode->i_gid = task->cred->egid;
rcu_read_lock();
cred = __task_cred(task);
inode->i_uid = cred->euid;
inode->i_gid = cred->egid;
rcu_read_unlock();
} else {
inode->i_uid = 0;
inode->i_gid = 0;
@ -1649,6 +1661,7 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
struct task_struct *task = get_proc_task(inode);
int fd = proc_fd(inode);
struct files_struct *files;
const struct cred *cred;
if (task) {
files = get_files_struct(task);
@ -1658,8 +1671,11 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
rcu_read_unlock();
put_files_struct(files);
if (task_dumpable(task)) {
inode->i_uid = task->cred->euid;
inode->i_gid = task->cred->egid;
rcu_read_lock();
cred = __task_cred(task);
inode->i_uid = cred->euid;
inode->i_gid = cred->egid;
rcu_read_unlock();
} else {
inode->i_uid = 0;
inode->i_gid = 0;