Commit 272ddc8b authored by Linus Torvalds's avatar Linus Torvalds
Browse files

proc: don't use FOLL_FORCE for reading cmdline and environment 



Now that Lorenzo cleaned things up and made the FOLL_FORCE users
explicit, it becomes obvious how some of them don't really need
FOLL_FORCE at all.

So remove FOLL_FORCE from the proc code that reads the command line and
arguments from user space.

The mem_rw() function actually does want FOLL_FORCE, because gdd (and
possibly many other debuggers) use it as a much more convenient version
of PTRACE_PEEKDATA, but we should consider making the FOLL_FORCE part
conditional on actually being a ptracer.  This does not actually do
that, just moves adds a comment to that effect and moves the gup_flags
settings next to each other.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 07d9a380

fs/proc/base.c

+8 −10
Original line number Diff line number Diff line
@@ -252,7 +252,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
	 * Inherently racy -- command line shares address space

	 * with code and data.

	 */

	rv = access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_FORCE);

	rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0);

	if (rv <= 0)

		goto out_free_page;
@@ -270,8 +270,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
			int nr_read;



			_count = min3(count, len, PAGE_SIZE);

			nr_read = access_remote_vm(mm, p, page, _count,

					FOLL_FORCE);

			nr_read = access_remote_vm(mm, p, page, _count, 0);

			if (nr_read < 0)

				rv = nr_read;

			if (nr_read <= 0)
@@ -306,8 +305,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, 
			bool final;



			_count = min3(count, len, PAGE_SIZE);

			nr_read = access_remote_vm(mm, p, page, _count,

					FOLL_FORCE);

			nr_read = access_remote_vm(mm, p, page, _count, 0);

			if (nr_read < 0)

				rv = nr_read;

			if (nr_read <= 0)
@@ -356,8 +354,7 @@ skip_argv: 
			bool final;



			_count = min3(count, len, PAGE_SIZE);

			nr_read = access_remote_vm(mm, p, page, _count,

					FOLL_FORCE);

			nr_read = access_remote_vm(mm, p, page, _count, 0);

			if (nr_read < 0)

				rv = nr_read;

			if (nr_read <= 0)
@@ -835,7 +832,7 @@ static ssize_t mem_rw(struct file *file, char __user *buf, 
	unsigned long addr = *ppos;

	ssize_t copied;

	char *page;

	unsigned int flags = FOLL_FORCE;

	unsigned int flags;



	if (!mm)

		return 0;
@@ -848,6 +845,8 @@ static ssize_t mem_rw(struct file *file, char __user *buf, 
	if (!atomic_inc_not_zero(&mm->mm_users))

		goto free;



	/* Maybe we should limit FOLL_FORCE to actual ptrace users? */

	flags = FOLL_FORCE;

	if (write)

		flags |= FOLL_WRITE;
@@ -971,8 +970,7 @@ static ssize_t environ_read(struct file *file, char __user *buf, 
		max_len = min_t(size_t, PAGE_SIZE, count);

		this_len = min(max_len, this_len);



		retval = access_remote_vm(mm, (env_start + src),

			page, this_len, FOLL_FORCE);

		retval = access_remote_vm(mm, (env_start + src), page, this_len, 0);



		if (retval <= 0) {

			ret = retval;

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