Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754771AbYKGAan (ORCPT ); Thu, 6 Nov 2008 19:30:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752323AbYKGAae (ORCPT ); Thu, 6 Nov 2008 19:30:34 -0500 Received: from smtp-out.google.com ([216.239.45.13]:22536 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751790AbYKGAad (ORCPT ); Thu, 6 Nov 2008 19:30:33 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:to:cc:subject:message-id:mime-version: content-type:content-disposition:in-reply-to:user-agent; b=Qrx68cDILheuMGPXXOYgyOIDVJB9mxdxLvfnizJW/5mCUmOlrGsOka4qvPtxly8OW OzhbXI47K963i7TY/6umw== Date: Thu, 6 Nov 2008 16:30:23 -0800 From: Ken Chen To: Ingo Molnar Cc: Alexey Dobriyan , linux-kernel@vger.kernel.org Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace Message-ID: <20081107003021.GA18666@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081106203520.GD3578@elte.hu> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4001 Lines: 123 On Thu, Nov 6, 2008 at 12:35 PM, Ingo Molnar 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 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 #include #include +#include #include #include #include @@ -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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/