lkml.org 
[lkml]   [2016]   [Sep]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 4/8] x86/dumpstack: Pin the target stack when dumping it
Date
Specifically, pin the stack in save_stack_trace_tsk() and
show_trace_log_lvl().

This will prevent a crash if the target task dies before or while
dumping its stack once we start freeing task stacks early.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/kernel/dumpstack_32.c | 5 +++++
arch/x86/kernel/dumpstack_64.c | 5 +++++
arch/x86/kernel/stacktrace.c | 5 +++++
3 files changed, 15 insertions(+)

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 2d65cfa5e0b4..122f37d7bb7e 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -163,6 +163,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack;
int i;

+ if (!try_get_task_stack(task))
+ return;
+
sp = sp ? : get_stack_pointer(task, regs);

stack = sp;
@@ -179,6 +182,8 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
}
pr_cont("\n");
show_trace_log_lvl(task, regs, sp, bp, log_lvl);
+
+ put_task_stack(task);
}


diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 8cb6004a4dfd..16c0d5f89b5e 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -218,6 +218,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack;
int i;

+ if (!try_get_task_stack(task))
+ return;
+
irq_stack_end = (unsigned long *)this_cpu_read(irq_stack_ptr);
irq_stack = irq_stack_end - (IRQ_STACK_SIZE / sizeof(long));

@@ -253,6 +256,8 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,

pr_cont("\n");
show_trace_log_lvl(task, regs, sp, bp, log_lvl);
+
+ put_task_stack(task);
}

void show_regs(struct pt_regs *regs)
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 785aef1c7ef5..23fa81e24c8a 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -79,9 +79,14 @@ void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)

void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
+ if (!try_get_task_stack(tsk))
+ return;
+
dump_trace(tsk, NULL, NULL, 0, &save_stack_ops_nosched, trace);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
+
+ put_task_stack(tsk);
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);

--
2.7.4
\
 
 \ /
  Last update: 2016-09-17 09:59    [W:0.129 / U:0.612 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site