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uprobes: Fix mmap_region()'s mm->mm_rb corruption if uprobe_mmap() fails

This patch fixes:

If mmap_region()->uprobe_mmap() fails, unmap_and_free_vma path
does unmap_region() but does not remove the soon-to-be-freed vma
from rb tree. Actually there are more problems but this is how
William noticed this bug.

Perhaps we could do do_munmap() + return in this case, but in
fact it is simply wrong to abort if uprobe_mmap() fails. Until
at least we move the !UPROBE_COPY_INSN code from
install_breakpoint() to uprobe_register().

For example, uprobe_mmap()->install_breakpoint() can fail if the
probed insn is not supported (remember, uprobe_register()
succeeds if nobody mmaps inode/offset), mmap() should not fail
in this case.

dup_mmap()->uprobe_mmap() is wrong too by the same reason,
fork() can race with uprobe_register() and fail for no reason if
it wins the race and does install_breakpoint() first.

And, if nothing else, both mmap_region() and dup_mmap() return
success if uprobe_mmap() fails. Change them to ignore the error
code from uprobe_mmap().

Reported-and-tested-by: William Cohen <>
Signed-off-by: Oleg Nesterov <>
Acked-by: Srikar Dronamraju <>
Cc: <> # v3.5
Cc: Anton Arapov <>
Cc: William Cohen <>
Cc: Linus Torvalds <>
Signed-off-by: Ingo Molnar <>
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1 parent 9160338 commit c7a3a88c938fbe3d70c2278e082b80eb830d1c58 @utrace utrace committed with Ingo Molnar Aug 19, 2012
Showing with 4 additions and 5 deletions.
  1. +2 −2 kernel/fork.c
  2. +2 −3 mm/mmap.c
@@ -455,8 +455,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
if (retval)
goto out;
- if (file && uprobe_mmap(tmp))
- goto out;
+ if (file)
+ uprobe_mmap(tmp);
/* a new mm has just been created */
arch_dup_mmap(oldmm, mm);
@@ -1356,9 +1356,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
} else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK))
make_pages_present(addr, addr + len);
- if (file && uprobe_mmap(vma))
- /* matching probes but cannot insert */
- goto unmap_and_free_vma;
+ if (file)
+ uprobe_mmap(vma);
return addr;

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