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Message-ID: <20081107003021.GA18666@google.com>
Date: Thu, 6 Nov 2008 16:30:23 -0800
From: Ken Chen <kenchen@...gle.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Alexey Dobriyan <adobriyan@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace
On Thu, Nov 6, 2008 at 12:35 PM, Ingo Molnar <mingo@...e.hu> wrote:
>> +static int proc_pid_stack(struct task_struct *task, char *buffer)
>> +{
>> + for (i = 0; i < trace.nr_entries; i++) {
>> + len += sprintf(buffer + len, "[<%p>] %pS\n",
>> + (void *)entries[i], (void
>> *)entries[i]);
>
> hm, this looks like a potential buffer overflow - isnt 'buffer' here
> only valid up to the next PAGE_SIZE boundary?
Yeah. the size of buffer allocated for printing is done at upper call
site in proc_info_read(). By the time we reach here, the size info is
lost. It would be too much churn to add a argument to the read method
of proc_op. Since these functions are all in one file, I moved
PROC_BLOCK_SIZE up so it can be used to check buffer length. Would
that be enough? Lots of other proc read methods don't check against
buffer overrun, I suppose those should be fixed as well.
updated patch that also fixed other comments.
Signed-off-by: Ken Chen <kenchen@...gle.com>
index bcceb99..11f5b75 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -139,6 +139,7 @@ Table 1-1: Process specific entries in /proc
statm Process memory status information
status Process status in human readable form
wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
+ stack Report full stack trace, enable via CONFIG_STACKTRACE
smaps Extension based on maps, the rss size for each mapped file
..............................................................................
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 486cf3f..8fb293d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -65,6 +65,7 @@
#include <linux/mm.h>
#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
+#include <linux/stacktrace.h>
#include <linux/resource.h>
#include <linux/module.h>
#include <linux/mount.h>
@@ -130,6 +131,12 @@ struct pid_entry {
{ .proc_show = &proc_##OTYPE } )
/*
+ * buffer size used for proc read. See proc_info_read().
+ * 4K page size but our output routines use some slack for overruns
+ */
+#define PROC_BLOCK_SIZE (3*1024)
+
+/*
* Count the number of hardlinks for the pid_entry table, excluding the .
* and .. links.
*/
@@ -340,6 +347,37 @@ static int proc_pid_wchan
}
#endif /* CONFIG_KALLSYMS */
+#ifdef CONFIG_STACKTRACE
+#define MAX_STACK_TRACE_DEPTH 64
+static int proc_pid_stack(struct task_struct *task, char *buffer)
+{
+ int i, len = 0;
+ unsigned long *entries;
+ struct stack_trace trace;
+
+ entries = kmalloc(sizeof(*entries) * MAX_STACK_TRACE_DEPTH, GFP_KERNEL);
+ if (!entries)
+ return -ENOMEM;
+
+ trace.nr_entries = 0;
+ trace.max_entries = MAX_STACK_TRACE_DEPTH;
+ trace.entries = entries;
+ trace.skip = 0;
+
+ read_lock(&tasklist_lock);
+ save_stack_trace_tsk(task, &trace);
+ read_unlock(&tasklist_lock);
+
+ for (i = 0; i < trace.nr_entries; i++) {
+ len += snprintf(buffer + len, PROC_BLOCK_SIZE - len,
+ "[<%p>] %pS\n",
+ (void *)entries[i], (void *)entries[i]);
+ }
+ kfree(entries);
+ return len;
+}
+#endif
+
#ifdef CONFIG_SCHEDSTATS
/*
* Provides /proc/PID/schedstat
@@ -688,8 +726,6 @@ static const struct file_operations proc_mountstats
.release = mounts_release,
};
-#define PROC_BLOCK_SIZE (3*1024) /* 4K page size but our output routines use some slack for overruns */
-
static ssize_t proc_info_read(struct file * file, char __user * buf,
size_t count, loff_t *ppos)
{
@@ -2491,6 +2527,9 @@ static const struct pid_entry tgid_base_stuff[] = {
#ifdef CONFIG_KALLSYMS
INF("wchan", S_IRUGO, pid_wchan),
#endif
+#ifdef CONFIG_STACKTRACE
+ INF("stack", S_IRUSR, pid_stack),
+#endif
#ifdef CONFIG_SCHEDSTATS
INF("schedstat", S_IRUGO, pid_schedstat),
#endif
--
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