From 77fc4af1b59d12ab3b1467adf0a5204806853123 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 29 May 2012 21:29:28 +0200 Subject: [PATCH] uprobes: Change register_for_each_vma() to take mm->mmap_sem for writing Change register_for_each_vma() to take mm->mmap_sem for writing. This is a bit unfortunate but hopefully not too bad, this is the slow path anyway. This is needed to ensure that find_active_uprobe() can not race with uprobe_register() which adds the new bp at the same bp_vaddr, after find_uprobe() fails and before is_swbp_at_addr_fast() checks the memory. IOW, this is needed to ensure that if find_active_uprobe() returns NULL but is_swbp == true, we can safely assume that it was the "normal" int3 and we should send SIGTRAP. There is another reason for this change. We are going to replace uprobes_state->count with MMF_ flags set by register/unregister and cleared by find_active_uprobe(), and set/clear shouldn't race with each other. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju Cc: Ananth N Mavinakayanahalli Cc: Anton Arapov Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20120529192928.GE8057@redhat.com Signed-off-by: Ingo Molnar --- kernel/events/uprobes.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index ee3df704e78a..a2ed82b4808c 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -853,12 +853,12 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register) } mm = vi->mm; - down_read(&mm->mmap_sem); + down_write(&mm->mmap_sem); vma = find_vma(mm, (unsigned long)vi->vaddr); if (!vma || !valid_vma(vma, is_register)) { list_del(&vi->probe_list); kfree(vi); - up_read(&mm->mmap_sem); + up_write(&mm->mmap_sem); mmput(mm); continue; } @@ -867,7 +867,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register) vaddr != vi->vaddr) { list_del(&vi->probe_list); kfree(vi); - up_read(&mm->mmap_sem); + up_write(&mm->mmap_sem); mmput(mm); continue; } @@ -877,7 +877,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register) else remove_breakpoint(uprobe, mm, vi->vaddr); - up_read(&mm->mmap_sem); + up_write(&mm->mmap_sem); mmput(mm); if (is_register) { if (ret && ret == -EEXIST) -- 2.30.2