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uprobes: Change write_opcode() to use FOLL_FORCE 

write_opcode()->get_user_pages() needs FOLL_FORCE to ensure we can
read the page even if the probed task did mprotect(PROT_NONE) after
uprobe_register(). Without FOLL_WRITE, FOLL_FORCE doesn't have any
side effect but allows to read the !VM_READ memory.

Otherwiese the subsequent uprobe_unregister()->set_orig_insn() fails
and we leak "int3". If that task does mprotect(PROT_READ | EXEC) and
execute the probed insn later it will be killed.

Note: in fact this is also needed for _register, see the next patch.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-09-16 17:20:06 +02:00
parent db023ea595
commit 75ed82ea53
1 changed files with 1 additions and 1 deletions
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2
kernel/events/uprobes.c
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@ -221,7 +221,7 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
retry:
/* Read the page with vaddr into memory */
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
if (ret <= 0)
return ret;