Messages in this thread Patch in this message | | | Date | Sun, 16 Sep 2012 19:52:48 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 3/3] uprobes: Restrict valid_vma(false) to skip VM_SHARED |
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valid_vma(false) ignores ->vm_flags, this is not actually right. We should never try to write into MAP_SHARED mapping, this can confuse an apllication which actually writes to ->vm_file.
With this patch valid_vma(false) ignores VM_WRITE only but checks other (immutable) bits checked by valid_vma(true). This can also speedup uprobe_munmap() and uprobe_unregister().
Note: even after this patch _unregister can confuse the probed application if it does mprotect(PROT_WRITE) after _register and installs "int3", but this is hardly possible to avoid and this doesn't differ from gdb case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/events/uprobes.c | 13 ++++--------- 1 files changed, 4 insertions(+), 9 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index b9b50dd..78364a2 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -100,17 +100,12 @@ struct uprobe { */ static bool valid_vma(struct vm_area_struct *vma, bool is_register) { - if (!vma->vm_file) - return false; - - if (!is_register) - return true; + vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED; - if ((vma->vm_flags & (VM_HUGETLB | VM_WRITE | VM_MAYEXEC | VM_SHARED)) - == VM_MAYEXEC) - return true; + if (is_register) + flags |= VM_WRITE; - return false; + return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC; } static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset) -- 1.5.5.1
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