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Commit 3673fb08 authored by Omar Sandoval's avatar Omar Sandoval Committed by Linus Torvalds
Browse files

proc/kcore: hold lock during read 

Now that we're using an rwsem, we can hold it during the entirety of
read_kcore() and have a common return path.  This is preparation for the
next change.

[akpm@linux-foundation.org: fix locking bug reported by Tetsuo Handa]
Link: http://lkml.kernel.org/r/d7cfbc1e8a76616f3b699eaff9df0a2730380534.1531953780.git.osandov@fb.com


Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: James Morse <james.morse@arm.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b66fb005

fs/proc/kcore.c

+40 −30
Original line number Diff line number Diff line
@@ -440,19 +440,18 @@ static ssize_t 
read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)

{

	char *buf = file->private_data;

	ssize_t acc = 0;

	size_t size, tsz;

	size_t elf_buflen;

	int nphdr;

	unsigned long start;

	size_t orig_buflen = buflen;

	int ret = 0;



	down_read(&kclist_lock);

	size = get_kcore_size(&nphdr, &elf_buflen);



	if (buflen == 0 || *fpos >= size) {

		up_read(&kclist_lock);

		return 0;

	}

	if (buflen == 0 || *fpos >= size)

		goto out;



	/* trim buflen to not go beyond EOF */

	if (buflen > size - *fpos)
@@ -465,28 +464,26 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) 
		tsz = elf_buflen - *fpos;

		if (buflen < tsz)

			tsz = buflen;

		elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);

		elf_buf = kzalloc(elf_buflen, GFP_KERNEL);

		if (!elf_buf) {

			up_read(&kclist_lock);

			return -ENOMEM;

			ret = -ENOMEM;

			goto out;

		}

		elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);

		up_read(&kclist_lock);

		if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {

			kfree(elf_buf);

			return -EFAULT;

			ret = -EFAULT;

			goto out;

		}

		kfree(elf_buf);

		buflen -= tsz;

		*fpos += tsz;

		buffer += tsz;

		acc += tsz;



		/* leave now if filled buffer already */

		if (buflen == 0)

			return acc;

	} else

		up_read(&kclist_lock);

			goto out;

	}



	/*

	 * Check to see if our file offset matches with any of
@@ -499,25 +496,29 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) 
	while (buflen) {

		struct kcore_list *m;



		down_read(&kclist_lock);

		list_for_each_entry(m, &kclist_head, list) {

			if (start >= m->addr && start < (m->addr+m->size))

				break;

		}

		up_read(&kclist_lock);



		if (&m->list == &kclist_head) {

			if (clear_user(buffer, tsz))

				return -EFAULT;

			if (clear_user(buffer, tsz)) {

				ret = -EFAULT;

				goto out;

			}

		} else if (m->type == KCORE_VMALLOC) {

			vread(buf, (char *)start, tsz);

			/* we have to zero-fill user buffer even if no read */

			if (copy_to_user(buffer, buf, tsz))

				return -EFAULT;

			if (copy_to_user(buffer, buf, tsz)) {

				ret = -EFAULT;

				goto out;

			}

		} else if (m->type == KCORE_USER) {

			/* User page is handled prior to normal kernel page: */

			if (copy_to_user(buffer, (char *)start, tsz))

				return -EFAULT;

			if (copy_to_user(buffer, (char *)start, tsz)) {

				ret = -EFAULT;

				goto out;

			}

		} else {

			if (kern_addr_valid(start)) {

				/*
@@ -525,26 +526,35 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) 
				 * hardened user copy kernel text checks.

				 */

				if (probe_kernel_read(buf, (void *) start, tsz)) {

					if (clear_user(buffer, tsz))

						return -EFAULT;

					if (clear_user(buffer, tsz)) {

						ret = -EFAULT;

						goto out;

					}

				} else {

					if (copy_to_user(buffer, buf, tsz))

						return -EFAULT;

					if (copy_to_user(buffer, buf, tsz)) {

						ret = -EFAULT;

						goto out;

					}

				}

			} else {

				if (clear_user(buffer, tsz))

					return -EFAULT;

				if (clear_user(buffer, tsz)) {

					ret = -EFAULT;

					goto out;

				}

			}

		}

		buflen -= tsz;

		*fpos += tsz;

		buffer += tsz;

		acc += tsz;

		start += tsz;

		tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);

	}



	return acc;

out:

	up_read(&kclist_lock);

	if (ret)

		return ret;

	return orig_buflen - buflen;

}