* Oleg Nesterov <[email protected]> [2012-08-08 19:37:37]: > uprobes_state->count is only needed to avoid the slow path in > uprobe_pre_sstep_notifier(). It is also checked in uprobe_munmap() > but ironically its only goal to decrement this counter. However, > it is very broken. Just some examples: > > - uprobe_mmap() can race with uprobe_unregister() and wrongly > increment the counter if it hits the non-uprobe "int3". Note > that install_breakpoint() checks ->consumers first and returns > -EEXIST if it is NULL. > > "atomic_sub() if error" in uprobe_mmap() looks obviously wrong > too. > > - uprobe_munmap() can race with uprobe_register() and wrongly > decrement the counter by the same reason. > > - Suppose an appication tries to increase the mmapped area via > sys_mremap(). vma_adjust() does uprobe_munmap(whole_vma) first, > this can nullify the counter temporarily and race with another > thread which can hit the bp, the application will be killed by > SIGTRAP. > > - Suppose an application mmaps 2 consecutive areas in the same file > and one (or both) of these areas has uprobes. In the likely case > mmap_region()->vma_merge() suceeds. Like above, this leads to > uprobe_munmap/uprobe_mmap from vma_merge()->vma_adjust() but then > mmap_region() does another uprobe_mmap(resulting_vma) and doubles > the counter. > > This patch only removes this counter and fixes the compile errors, > then we will try to cleanup the changed code and add something else > instead. > > Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Srikar Dronamraju <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
