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uprobes: Change read_opcode() to use FOLL_FORCE 

set_orig_insn()->read_opcode() should not fail if the probed
task did mprotect() after uprobe_register(), change it to use
FOLL_FORCE. Without FOLL_WRITE this doesn't have any "side"
effect but allows to read the !VM_READ memory.

There is another reason for this change, we are going to use
is_swbp_at_addr() from handle_swbp() which can race with another
thread doing mprotect().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192759.GB8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2012-05-29 21:27:59 +02:00 committed by Ingo Molnar
parent c00b275043
commit a3d7bb4793
1 changed files with 1 additions and 1 deletions
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2
kernel/events/uprobes.c
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@ -312,7 +312,7 @@ static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_
void *vaddr_new;
int ret;
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (ret <= 0)
return ret;