Commit aa1f1a63 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

lib/syscall: Pin the task stack in collect_syscall()

This will avoid a potential read-after-free if collect_syscall()
(e.g. /proc/PID/syscall) is called on an exiting task.
Reported-by: default avatarJann Horn <>
Signed-off-by: default avatarAndy Lutomirski <>
Cc: Borislav Petkov <>
Cc: Brian Gerst <>
Cc: Denys Vlasenko <>
Cc: H. Peter Anvin <>
Cc: Josh Poimboeuf <>
Cc: Linus Torvalds <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Link: default avatarIngo Molnar <>
parent 74327a3e
......@@ -7,9 +7,19 @@ static int collect_syscall(struct task_struct *target, long *callno,
unsigned long args[6], unsigned int maxargs,
unsigned long *sp, unsigned long *pc)
struct pt_regs *regs = task_pt_regs(target);
if (unlikely(!regs))
struct pt_regs *regs;
if (!try_get_task_stack(target)) {
/* Task has no stack, so the task isn't in a syscall. */
*callno = -1;
return 0;
regs = task_pt_regs(target);
if (unlikely(!regs)) {
return -EAGAIN;
*sp = user_stack_pointer(regs);
*pc = instruction_pointer(regs);
......@@ -18,6 +28,7 @@ static int collect_syscall(struct task_struct *target, long *callno,
if (*callno != -1L && maxargs > 0)
syscall_get_arguments(target, regs, 0, maxargs, args);
return 0;
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