From a9712bc12c40c172e393f85a9b2ba8db4bf59509 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 23 Mar 2011 15:52:50 -0400 Subject: [PATCH] deal with races in /proc/*/{syscall,stack,personality} All of those are rw-r--r-- and all are broken for suid - if you open a file before the target does suid-root exec, you'll be still able to access it. For personality it's not a big deal, but for syscall and stack it's a real problem. Fix: check that task is tracable for you at the time of read(). Signed-off-by: Al Viro --- fs/proc/base.c | 69 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 50 insertions(+), 19 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index bc15df390ec..7d5bb8b9a4f 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -347,6 +347,23 @@ static int proc_pid_wchan(struct task_struct *task, char *buffer) } #endif /* CONFIG_KALLSYMS */ +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)) { + mutex_unlock(&task->signal->cred_guard_mutex); + return -EPERM; + } + return 0; +} + +static void unlock_trace(struct task_struct *task) +{ + mutex_unlock(&task->signal->cred_guard_mutex); +} + #ifdef CONFIG_STACKTRACE #define MAX_STACK_TRACE_DEPTH 64 @@ -356,6 +373,7 @@ static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns, { struct stack_trace trace; unsigned long *entries; + int err; int i; entries = kmalloc(MAX_STACK_TRACE_DEPTH * sizeof(*entries), GFP_KERNEL); @@ -366,15 +384,20 @@ static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns, trace.max_entries = MAX_STACK_TRACE_DEPTH; trace.entries = entries; trace.skip = 0; - save_stack_trace_tsk(task, &trace); - for (i = 0; i < trace.nr_entries; i++) { - seq_printf(m, "[<%p>] %pS\n", - (void *)entries[i], (void *)entries[i]); + err = lock_trace(task); + if (!err) { + save_stack_trace_tsk(task, &trace); + + for (i = 0; i < trace.nr_entries; i++) { + seq_printf(m, "[<%p>] %pS\n", + (void *)entries[i], (void *)entries[i]); + } + unlock_trace(task); } kfree(entries); - return 0; + return err; } #endif @@ -537,18 +560,22 @@ static int proc_pid_syscall(struct task_struct *task, char *buffer) { long nr; unsigned long args[6], sp, pc; + int res = lock_trace(task); + if (res) + return res; if (task_current_syscall(task, &nr, args, 6, &sp, &pc)) - return sprintf(buffer, "running\n"); - - if (nr < 0) - return sprintf(buffer, "%ld 0x%lx 0x%lx\n", nr, sp, pc); - - return sprintf(buffer, + res = sprintf(buffer, "running\n"); + else if (nr < 0) + res = sprintf(buffer, "%ld 0x%lx 0x%lx\n", nr, sp, pc); + else + res = sprintf(buffer, "%ld 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n", nr, args[0], args[1], args[2], args[3], args[4], args[5], sp, pc); + unlock_trace(task); + return res; } #endif /* CONFIG_HAVE_ARCH_TRACEHOOK */ @@ -2775,8 +2802,12 @@ static int proc_tgid_io_accounting(struct task_struct *task, char *buffer) static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) { - seq_printf(m, "%08x\n", task->personality); - return 0; + int err = lock_trace(task); + if (!err) { + seq_printf(m, "%08x\n", task->personality); + unlock_trace(task); + } + return err; } /* @@ -2795,7 +2826,7 @@ static const struct pid_entry tgid_base_stuff[] = { REG("environ", S_IRUSR, proc_environ_operations), INF("auxv", S_IRUSR, proc_pid_auxv), ONE("status", S_IRUGO, proc_pid_status), - ONE("personality", S_IRUSR, proc_pid_personality), + ONE("personality", S_IRUGO, proc_pid_personality), INF("limits", S_IRUGO, proc_pid_limits), #ifdef CONFIG_SCHED_DEBUG REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations), @@ -2805,7 +2836,7 @@ static const struct pid_entry tgid_base_stuff[] = { #endif REG("comm", S_IRUGO|S_IWUSR, proc_pid_set_comm_operations), #ifdef CONFIG_HAVE_ARCH_TRACEHOOK - INF("syscall", S_IRUSR, proc_pid_syscall), + INF("syscall", S_IRUGO, proc_pid_syscall), #endif INF("cmdline", S_IRUGO, proc_pid_cmdline), ONE("stat", S_IRUGO, proc_tgid_stat), @@ -2833,7 +2864,7 @@ static const struct pid_entry tgid_base_stuff[] = { INF("wchan", S_IRUGO, proc_pid_wchan), #endif #ifdef CONFIG_STACKTRACE - ONE("stack", S_IRUSR, proc_pid_stack), + ONE("stack", S_IRUGO, proc_pid_stack), #endif #ifdef CONFIG_SCHEDSTATS INF("schedstat", S_IRUGO, proc_pid_schedstat), @@ -3135,14 +3166,14 @@ static const struct pid_entry tid_base_stuff[] = { REG("environ", S_IRUSR, proc_environ_operations), INF("auxv", S_IRUSR, proc_pid_auxv), ONE("status", S_IRUGO, proc_pid_status), - ONE("personality", S_IRUSR, proc_pid_personality), + ONE("personality", S_IRUGO, proc_pid_personality), INF("limits", S_IRUGO, proc_pid_limits), #ifdef CONFIG_SCHED_DEBUG REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations), #endif REG("comm", S_IRUGO|S_IWUSR, proc_pid_set_comm_operations), #ifdef CONFIG_HAVE_ARCH_TRACEHOOK - INF("syscall", S_IRUSR, proc_pid_syscall), + INF("syscall", S_IRUGO, proc_pid_syscall), #endif INF("cmdline", S_IRUGO, proc_pid_cmdline), ONE("stat", S_IRUGO, proc_tid_stat), @@ -3169,7 +3200,7 @@ static const struct pid_entry tid_base_stuff[] = { INF("wchan", S_IRUGO, proc_pid_wchan), #endif #ifdef CONFIG_STACKTRACE - ONE("stack", S_IRUSR, proc_pid_stack), + ONE("stack", S_IRUGO, proc_pid_stack), #endif #ifdef CONFIG_SCHEDSTATS INF("schedstat", S_IRUGO, proc_pid_schedstat), -- 2.20.1