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Commit 29dedee0 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Add mem_cgroup_charge_anon() into uprobe_write_opcode() 



Hugh says:

    The one I noticed was that it forgets all about memcg (because
    it was copied from KSM, and there the replacement page has already
    been charged to a memcg). See how mm/memory.c do_anonymous_page()
    does a mem_cgroup_charge_anon().

Hopefully not a big problem, uprobes is a system-wide thing and only
root can insert the probes. But I agree, should be fixed anyway.

Add mem_cgroup_{un,}charge_anon() into uprobe_write_opcode(). To simplify
the error handling (and avoid the new "uncharge" label) the patch also
moves anon_vma_prepare() up before we alloc/charge the new page.

While at it fix the comment about ->mmap_sem, it is held for write.

Suggested-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 8e02ae57

kernel/events/uprobes.c

+11 −12
Original line number Diff line number Diff line
@@ -279,18 +279,13 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t 
 * supported by that architecture then we need to modify is_trap_at_addr and

 * uprobe_write_opcode accordingly. This would never be a problem for archs

 * that have fixed length instructions.

 */



/*

 *

 * uprobe_write_opcode - write the opcode at a given virtual address.

 * @mm: the probed process address space.

 * @vaddr: the virtual address to store the opcode.

 * @opcode: opcode to be written at @vaddr.

 *

 * Called with mm->mmap_sem held (for read and with a reference to

 * mm).

 *

 * For mm @mm, write the opcode at @vaddr.

 * Called with mm->mmap_sem held for write.

 * Return 0 (success) or a negative errno.

 */

int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr,
@@ -310,21 +305,25 @@ int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr, 
	if (ret <= 0)

		goto put_old;



	ret = anon_vma_prepare(vma);

	if (ret)

		goto put_old;



	ret = -ENOMEM;

	new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);

	if (!new_page)

		goto put_old;



	__SetPageUptodate(new_page);

	if (mem_cgroup_charge_anon(new_page, mm, GFP_KERNEL))

		goto put_new;



	__SetPageUptodate(new_page);

	copy_highpage(new_page, old_page);

	copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);



	ret = anon_vma_prepare(vma);

	if (ret)

		goto put_new;



	ret = __replace_page(vma, vaddr, old_page, new_page);

	if (ret)

		mem_cgroup_uncharge_page(new_page);



put_new:

	page_cache_release(new_page);