Commit 3cb4a0bb authored by Kawai, Hidehiro's avatar Kawai, Hidehiro Committed by Linus Torvalds
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coredump masking: add an interface for core dump filter 



This patch adds an interface to set/reset flags which determines each memory
segment should be dumped or not when a core file is generated.

/proc/<pid>/coredump_filter file is provided to access the flags.  You can
change the flag status for a particular process by writing to or reading from
the file.

The flag status is inherited to the child process when it is created.

Signed-off-by: default avatarHidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6c5d5238

fs/proc/base.c

+89 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ 
#include <linux/poll.h>

#include <linux/nsproxy.h>

#include <linux/oom.h>

#include <linux/elf.h>

#include "internal.h"



/* NOTE:
@@ -1785,6 +1786,91 @@ static const struct inode_operations proc_attr_dir_inode_operations = { 


#endif



#if defined(USE_ELF_CORE_DUMP) && defined(CONFIG_ELF_CORE)

static ssize_t proc_coredump_filter_read(struct file *file, char __user *buf,

					 size_t count, loff_t *ppos)

{

	struct task_struct *task = get_proc_task(file->f_dentry->d_inode);

	struct mm_struct *mm;

	char buffer[PROC_NUMBUF];

	size_t len;

	int ret;



	if (!task)

		return -ESRCH;



	ret = 0;

	mm = get_task_mm(task);

	if (mm) {

		len = snprintf(buffer, sizeof(buffer), "%08lx\n",

			       ((mm->flags & MMF_DUMP_FILTER_MASK) >>

				MMF_DUMP_FILTER_SHIFT));

		mmput(mm);

		ret = simple_read_from_buffer(buf, count, ppos, buffer, len);

	}



	put_task_struct(task);



	return ret;

}



static ssize_t proc_coredump_filter_write(struct file *file,

					  const char __user *buf,

					  size_t count,

					  loff_t *ppos)

{

	struct task_struct *task;

	struct mm_struct *mm;

	char buffer[PROC_NUMBUF], *end;

	unsigned int val;

	int ret;

	int i;

	unsigned long mask;



	ret = -EFAULT;

	memset(buffer, 0, sizeof(buffer));

	if (count > sizeof(buffer) - 1)

		count = sizeof(buffer) - 1;

	if (copy_from_user(buffer, buf, count))

		goto out_no_task;



	ret = -EINVAL;

	val = (unsigned int)simple_strtoul(buffer, &end, 0);

	if (*end == '\n')

		end++;

	if (end - buffer == 0)

		goto out_no_task;



	ret = -ESRCH;

	task = get_proc_task(file->f_dentry->d_inode);

	if (!task)

		goto out_no_task;



	ret = end - buffer;

	mm = get_task_mm(task);

	if (!mm)

		goto out_no_mm;



	for (i = 0, mask = 1; i < MMF_DUMP_FILTER_BITS; i++, mask <<= 1) {

		if (val & mask)

			set_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);

		else

			clear_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);

	}



	mmput(mm);

 out_no_mm:

	put_task_struct(task);

 out_no_task:

	return ret;

}



static const struct file_operations proc_coredump_filter_operations = {

	.read		= proc_coredump_filter_read,

	.write		= proc_coredump_filter_write,

};

#endif



/*

 * /proc/self:

 */
@@ -2005,6 +2091,9 @@ static const struct pid_entry tgid_base_stuff[] = { 
#ifdef CONFIG_FAULT_INJECTION

	REG("make-it-fail", S_IRUGO|S_IWUSR, fault_inject),

#endif

#if defined(USE_ELF_CORE_DUMP) && defined(CONFIG_ELF_CORE)

	REG("coredump_filter", S_IRUGO|S_IWUSR, coredump_filter),

#endif

#ifdef CONFIG_TASK_IO_ACCOUNTING

	INF("io",	S_IRUGO, pid_io_accounting),

#endif

include/linux/sched.h

+14 −0
Original line number Diff line number Diff line
@@ -349,8 +349,22 @@ extern void set_dumpable(struct mm_struct *mm, int value); 
extern int get_dumpable(struct mm_struct *mm);



/* mm flags */

/* dumpable bits */

#define MMF_DUMPABLE      0  /* core dump is permitted */

#define MMF_DUMP_SECURELY 1  /* core file is readable only by root */

#define MMF_DUMPABLE_BITS 2



/* coredump filter bits */

#define MMF_DUMP_ANON_PRIVATE	2

#define MMF_DUMP_ANON_SHARED	3

#define MMF_DUMP_MAPPED_PRIVATE	4

#define MMF_DUMP_MAPPED_SHARED	5

#define MMF_DUMP_FILTER_SHIFT	MMF_DUMPABLE_BITS

#define MMF_DUMP_FILTER_BITS	4

#define MMF_DUMP_FILTER_MASK \

	(((1 << MMF_DUMP_FILTER_BITS) - 1) << MMF_DUMP_FILTER_SHIFT)

#define MMF_DUMP_FILTER_DEFAULT \

	((1 << MMF_DUMP_ANON_PRIVATE) |	(1 << MMF_DUMP_ANON_SHARED))



struct mm_struct {

	struct vm_area_struct * mmap;		/* list of VMAs */

kernel/fork.c

+2 −0
Original line number Diff line number Diff line
@@ -334,6 +334,8 @@ static struct mm_struct * mm_init(struct mm_struct * mm) 
	atomic_set(&mm->mm_count, 1);

	init_rwsem(&mm->mmap_sem);

	INIT_LIST_HEAD(&mm->mmlist);

	mm->flags = (current->mm) ? current->mm->flags

				  : MMF_DUMP_FILTER_DEFAULT;

	mm->core_waiters = 0;

	mm->nr_ptes = 0;

	set_mm_counter(mm, file_rss, 0);

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