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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: Hugh Dickins <hughd@google.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
This commit is contained in:
Oleg Nesterov 2014-05-05 16:38:18 +02:00
parent 8e02ae573e
commit 29dedee0e6
1 changed files with 11 additions and 12 deletions
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23
kernel/events/uprobes.c
View File

@ -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 @@ retry:
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);