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-rw-r--r--fs/proc/array.c2
-rw-r--r--fs/proc/base.c20
-rw-r--r--fs/proc/namespaces.c4
-rw-r--r--include/linux/ptrace.h24
-rw-r--r--kernel/events/core.c2
-rw-r--r--kernel/futex.c2
-rw-r--r--kernel/futex_compat.c2
-rw-r--r--kernel/kcmp.c4
-rw-r--r--kernel/ptrace.c39
-rw-r--r--mm/process_vm_access.c2
-rw-r--r--security/commoncap.c7
11 files changed, 79 insertions, 29 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c
index baf3464bbce0..ca4a64b4b119 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -391,7 +391,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
state = *get_task_state(task);
vsize = eip = esp = 0;
- permitted = ptrace_may_access(task, PTRACE_MODE_READ | PTRACE_MODE_NOAUDIT);
+ permitted = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT);
mm = get_task_mm(task);
if (mm) {
vsize = task_vsize(mm);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 489ba8caafc0..be78847782c4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -239,7 +239,7 @@ out:
static int proc_pid_auxv(struct task_struct *task, char *buffer)
{
- struct mm_struct *mm = mm_access(task, PTRACE_MODE_READ);
+ struct mm_struct *mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
int res = PTR_ERR(mm);
if (mm && !IS_ERR(mm)) {
unsigned int nwords = 0;
@@ -269,7 +269,7 @@ static int proc_pid_wchan(struct task_struct *task, char *buffer)
wchan = get_wchan(task);
if (lookup_symbol_name(wchan, symname) < 0)
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
return 0;
else
return sprintf(buffer, "%lu", wchan);
@@ -283,7 +283,7 @@ static int lock_trace(struct task_struct *task)
int err = mutex_lock_killable(&task->signal->cred_guard_mutex);
if (err)
return err;
- if (!ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
+ if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
mutex_unlock(&task->signal->cred_guard_mutex);
return -EPERM;
}
@@ -557,7 +557,7 @@ static int proc_fd_access_allowed(struct inode *inode)
*/
task = get_proc_task(inode);
if (task) {
- allowed = ptrace_may_access(task, PTRACE_MODE_READ);
+ allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
put_task_struct(task);
}
return allowed;
@@ -592,7 +592,7 @@ static bool has_pid_permissions(struct pid_namespace *pid,
return true;
if (in_group_p(pid->pid_gid))
return true;
- return ptrace_may_access(task, PTRACE_MODE_READ);
+ return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
}
@@ -707,7 +707,7 @@ static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
if (!task)
return -ESRCH;
- mm = mm_access(task, mode);
+ mm = mm_access(task, mode | PTRACE_MODE_FSCREDS);
put_task_struct(task);
if (IS_ERR(mm))
@@ -1760,7 +1760,7 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags)
if (!task)
goto out_notask;
- mm = mm_access(task, PTRACE_MODE_READ);
+ mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
if (IS_ERR_OR_NULL(mm))
goto out;
@@ -1895,7 +1895,7 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
goto out;
result = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out_put_task;
result = -ENOENT;
@@ -1952,7 +1952,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
goto out;
ret = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out_put_task;
ret = 0;
@@ -2431,7 +2431,7 @@ static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
if (result)
return result;
- if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
result = -EACCES;
goto out_unlock;
}
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 9ae46b87470d..a05ed26075e3 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -119,7 +119,7 @@ static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd)
if (!task)
goto out;
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out_put_task;
ns_path.dentry = proc_ns_get_dentry(sb, task, ei->ns.ns_ops);
@@ -152,7 +152,7 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
if (!task)
goto out;
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out_put_task;
len = -ENOENT;
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index cc79eff4a1ad..608d90444b6f 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -56,7 +56,29 @@ extern void exit_ptrace(struct task_struct *tracer);
#define PTRACE_MODE_READ 0x01
#define PTRACE_MODE_ATTACH 0x02
#define PTRACE_MODE_NOAUDIT 0x04
-/* Returns true on success, false on denial. */
+#define PTRACE_MODE_FSCREDS 0x08
+#define PTRACE_MODE_REALCREDS 0x10
+
+/* shorthands for READ/ATTACH and FSCREDS/REALCREDS combinations */
+#define PTRACE_MODE_READ_FSCREDS (PTRACE_MODE_READ | PTRACE_MODE_FSCREDS)
+#define PTRACE_MODE_READ_REALCREDS (PTRACE_MODE_READ | PTRACE_MODE_REALCREDS)
+#define PTRACE_MODE_ATTACH_FSCREDS (PTRACE_MODE_ATTACH | PTRACE_MODE_FSCREDS)
+#define PTRACE_MODE_ATTACH_REALCREDS (PTRACE_MODE_ATTACH | PTRACE_MODE_REALCREDS)
+
+/**
+ * ptrace_may_access - check whether the caller is permitted to access
+ * a target task.
+ * @task: target task
+ * @mode: selects type of access and caller credentials
+ *
+ * Returns true on success, false on denial.
+ *
+ * One of the flags PTRACE_MODE_FSCREDS and PTRACE_MODE_REALCREDS must
+ * be set in @mode to specify whether the access was requested through
+ * a filesystem syscall (should use effective capabilities and fsuid
+ * of the caller) or through an explicit syscall such as
+ * process_vm_writev or ptrace (and should use the real credentials).
+ */
extern bool ptrace_may_access(struct task_struct *task, unsigned int mode);
static inline int ptrace_reparented(struct task_struct *child)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 169cc28642ba..bfd91336e888 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3096,7 +3096,7 @@ find_lively_task_by_vpid(pid_t vpid)
/* Reuse ptrace permission checks for now. */
err = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
goto errout;
return task;
diff --git a/kernel/futex.c b/kernel/futex.c
index fda2950f2ce4..ad9274232d28 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2774,7 +2774,7 @@ SYSCALL_DEFINE3(get_robust_list, int, pid,
}
ret = -EPERM;
- if (!ptrace_may_access(p, PTRACE_MODE_READ))
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
goto err_unlock;
head = p->robust_list;
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index f9f44fd4d34d..3888617a1f9e 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -155,7 +155,7 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
}
ret = -EPERM;
- if (!ptrace_may_access(p, PTRACE_MODE_READ))
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
goto err_unlock;
head = p->compat_robust_list;
diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index 0aa69ea1d8fd..3a47fa998fe0 100644
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -122,8 +122,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
&task2->signal->cred_guard_mutex);
if (ret)
goto err;
- if (!ptrace_may_access(task1, PTRACE_MODE_READ) ||
- !ptrace_may_access(task2, PTRACE_MODE_READ)) {
+ if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
+ !ptrace_may_access(task2, PTRACE_MODE_READ_REALCREDS)) {
ret = -EPERM;
goto err_unlock;
}
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index be9760f8284a..4524314ecbb4 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -225,6 +225,14 @@ static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
{
const struct cred *cred = current_cred(), *tcred;
+ int dumpable = 0;
+ kuid_t caller_uid;
+ kgid_t caller_gid;
+
+ if (!(mode & PTRACE_MODE_FSCREDS) == !(mode & PTRACE_MODE_REALCREDS)) {
+ WARN(1, "denying ptrace access check without PTRACE_MODE_*CREDS\n");
+ return -EPERM;
+ }
/* May we inspect the given task?
* This check is used both for attaching with ptrace
@@ -234,18 +242,33 @@ static 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.
*/
- int dumpable = 0;
+
/* Don't let security modules deny introspection */
if (same_thread_group(task, current))
return 0;
rcu_read_lock();
+ if (mode & PTRACE_MODE_FSCREDS) {
+ caller_uid = cred->fsuid;
+ caller_gid = cred->fsgid;
+ } else {
+ /*
+ * Using the euid would make more sense here, but something
+ * in userland might rely on the old behavior, and this
+ * shouldn't be a security problem since
+ * PTRACE_MODE_REALCREDS implies that the caller explicitly
+ * used a syscall that requests access to another process
+ * (and not a filesystem syscall to procfs).
+ */
+ caller_uid = cred->uid;
+ caller_gid = cred->gid;
+ }
tcred = __task_cred(task);
- if (uid_eq(cred->uid, tcred->euid) &&
- uid_eq(cred->uid, tcred->suid) &&
- uid_eq(cred->uid, tcred->uid) &&
- gid_eq(cred->gid, tcred->egid) &&
- gid_eq(cred->gid, tcred->sgid) &&
- gid_eq(cred->gid, tcred->gid))
+ if (uid_eq(caller_uid, tcred->euid) &&
+ uid_eq(caller_uid, tcred->suid) &&
+ uid_eq(caller_uid, tcred->uid) &&
+ gid_eq(caller_gid, tcred->egid) &&
+ gid_eq(caller_gid, tcred->sgid) &&
+ gid_eq(caller_gid, tcred->gid))
goto ok;
if (ptrace_has_cap(tcred->user_ns, mode))
goto ok;
@@ -312,7 +335,7 @@ static int ptrace_attach(struct task_struct *task, long request,
goto out;
task_lock(task);
- retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
+ retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS);
task_unlock(task);
if (retval)
goto unlock_creds;
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index fd26d0433509..e739825be8b3 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -298,7 +298,7 @@ static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
goto free_proc_pages;
}
- mm = mm_access(task, PTRACE_MODE_ATTACH);
+ mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
if (!mm || IS_ERR(mm)) {
rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
/*
diff --git a/security/commoncap.c b/security/commoncap.c
index 963dc5981661..a484506445d7 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -142,12 +142,17 @@ int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
{
int ret = 0;
const struct cred *cred, *child_cred;
+ const kernel_cap_t *caller_caps;
rcu_read_lock();
cred = current_cred();
child_cred = __task_cred(child);
+ if (mode & PTRACE_MODE_FSCREDS)
+ caller_caps = &cred->cap_effective;
+ else
+ caller_caps = &cred->cap_permitted;
if (cred->user_ns == child_cred->user_ns &&
- cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
+ cap_issubset(child_cred->cap_permitted, *caller_caps))
goto out;
if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
goto out;