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-rw-r--r--fs/proc/array.c2
-rw-r--r--fs/proc/base.c12
-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/ptrace.c39
-rw-r--r--mm/process_vm_access.c2
-rw-r--r--security/commoncap.c7
10 files changed, 73 insertions, 23 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 439b5a1048c9..b83dcbb83d3f 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -380,7 +380,7 @@ 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);
+ permitted = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
mm = get_task_mm(task);
if (mm) {
vsize = task_vsize(mm);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 2c38a3e4fa51..9bc4643054bf 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -216,7 +216,7 @@ static struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
struct mm_struct *mm_for_maps(struct task_struct *task)
{
- return mm_access(task, PTRACE_MODE_READ);
+ return mm_access(task, PTRACE_MODE_READ_FSCREDS);
}
static int proc_pid_cmdline(struct task_struct *task, char * buffer)
@@ -288,7 +288,7 @@ 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);
@@ -302,7 +302,7 @@ 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;
}
@@ -544,7 +544,7 @@ 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;
@@ -769,7 +769,7 @@ static int mem_open(struct inode* inode, struct file* file)
if (!task)
return -ESRCH;
- mm = mm_access(task, PTRACE_MODE_ATTACH);
+ mm = mm_access(task, PTRACE_MODE_ATTACH | PTRACE_MODE_FSCREDS);
put_task_struct(task);
if (IS_ERR(mm))
@@ -2627,7 +2627,7 @@ 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 d6c078ea1489..50de28b0a670 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -91,7 +91,7 @@ static int proc_ns_dir_readdir(struct file *filp, void *dirent,
goto out_no_task;
ret = -EPERM;
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out;
ret = 0;
@@ -154,7 +154,7 @@ static struct dentry *proc_ns_dir_lookup(struct inode *dir,
goto out_no_task;
error = ERR_PTR(-EPERM);
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out;
last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index e49240ba8346..953193651aa8 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -130,9 +130,31 @@ extern void __ptrace_unlink(struct task_struct *child);
extern void exit_ptrace(struct task_struct *tracer);
#define PTRACE_MODE_READ 1
#define PTRACE_MODE_ATTACH 2
+#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)
+
/* Returns 0 on success, -errno on denial. */
extern int __ptrace_may_access(struct task_struct *task, unsigned int mode);
-/* Returns true on success, false on denial. */
+/**
+ * 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 cd4f88a39fe1..bc94278e0b45 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3004,7 +3004,7 @@ 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 bbd360110079..3854e754f641 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2627,7 +2627,7 @@ 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 a9642d528630..e07b64b465fc 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -154,7 +154,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
}
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/ptrace.c b/kernel/ptrace.c
index fd3909b87188..b50cded5b80e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -220,6 +220,14 @@ int ptrace_check_attach(struct task_struct *child, bool ignore_state)
int __ptrace_may_access(struct task_struct *task, unsigned int mode)
{
const struct cred *cred = current_cred(), *tcred;
+ int dumpable = 0;
+ uid_t caller_uid;
+ gid_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
@@ -229,19 +237,34 @@ 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 (cred->user->user_ns == tcred->user->user_ns &&
- (cred->uid == tcred->euid &&
- cred->uid == tcred->suid &&
- cred->uid == tcred->uid &&
- cred->gid == tcred->egid &&
- cred->gid == tcred->sgid &&
- cred->gid == tcred->gid))
+ (caller_uid == tcred->euid &&
+ caller_uid == tcred->suid &&
+ caller_uid == tcred->uid &&
+ caller_gid == tcred->egid &&
+ caller_gid == tcred->sgid &&
+ caller_gid == tcred->gid))
goto ok;
if (ns_capable(tcred->user->user_ns, CAP_SYS_PTRACE))
goto ok;
@@ -308,7 +331,7 @@ 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 70e814a4d0b8..88c35c9e4407 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -299,7 +299,7 @@ static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
}
task_lock(task);
- if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
+ if (__ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS)) {
task_unlock(task);
rc = -EPERM;
goto put_task_struct;
diff --git a/security/commoncap.c b/security/commoncap.c
index 12440ee03c31..4f338aba1ddb 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -141,12 +141,17 @@ 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->user_ns == child_cred->user->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->user_ns, CAP_SYS_PTRACE))
goto out;
generated by cgit v1.2.3 (git 2.46.0) at 2025-09-26 17:44:33 +0000