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uprobes: Fix mmap_region()'s mm->mm_rb corruption if uprobe_mmap() fails
This patch fixes: https://bugzilla.redhat.com/show_bug.cgi?id=843640 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 <firstname.lastname@example.org> Signed-off-by: Oleg Nesterov <email@example.com> Acked-by: Srikar Dronamraju <firstname.lastname@example.org> Cc: <email@example.com> # v3.5 Cc: Anton Arapov <firstname.lastname@example.org> Cc: William Cohen <email@example.com> Cc: Linus Torvalds <firstname.lastname@example.org> Link: http://lkml.kernel.org/r/20120819171042.GB26957@redhat.com Signed-off-by: Ingo Molnar <email@example.com>
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