uprobes/core: Decrement uprobe count before the pages are unmapped
Uprobes has a callback (uprobe_munmap()) in the unmap path to
maintain the uprobes count.
In the exit path this callback gets called in unlink_file_vma().
However by the time unlink_file_vma() is called, the pages would
have been unmapped (in unmap_vmas()) and the task->rss_stat counts
accounted (in zap_pte_range()).
If the exiting process has probepoints, uprobe_munmap() checks if
the breakpoint instruction was around before decrementing the probe
count.
This results in a file backed page being reread by uprobe_munmap()
and hence it does not find the breakpoint.
This patch fixes this problem by moving the callback to
unmap_single_vma(). Since unmap_single_vma() may not unmap the
complete vma, add start and end parameters to uprobe_munmap().
This bug became apparent courtesy of commit c3f0327f8e
("mm: add rss counters consistency check").
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120411103527.23245.9835.sendpatchset@srdronam.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
parent
7396fa818d
commit
cbc91f71b5
4 changed files with 12 additions and 8 deletions
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@ -107,7 +107,7 @@ extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
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extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
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extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
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extern int uprobe_mmap(struct vm_area_struct *vma);
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extern void uprobe_munmap(struct vm_area_struct *vma);
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extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
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extern void uprobe_free_utask(struct task_struct *t);
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extern void uprobe_copy_process(struct task_struct *t);
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extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
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@ -134,7 +134,8 @@ static inline int uprobe_mmap(struct vm_area_struct *vma)
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{
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return 0;
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}
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static inline void uprobe_munmap(struct vm_area_struct *vma)
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static inline void
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uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
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{
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}
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static inline void uprobe_notify_resume(struct pt_regs *regs)
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@ -1112,7 +1112,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
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/*
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* Called in context of a munmap of a vma.
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*/
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void uprobe_munmap(struct vm_area_struct *vma)
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void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
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{
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struct list_head tmp_list;
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struct uprobe *uprobe, *u;
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@ -1138,7 +1138,7 @@ void uprobe_munmap(struct vm_area_struct *vma)
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list_del(&uprobe->pending_list);
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vaddr = vma_address(vma, uprobe->offset);
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if (vaddr >= vma->vm_start && vaddr < vma->vm_end) {
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if (vaddr >= start && vaddr < end) {
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/*
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* An unregister could have removed the probe before
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* unmap. So check before we decrement the count.
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@ -1307,6 +1307,9 @@ static void unmap_single_vma(struct mmu_gather *tlb,
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if (end <= vma->vm_start)
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return;
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if (vma->vm_file)
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uprobe_munmap(vma, start, end);
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if (vma->vm_flags & VM_ACCOUNT)
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*nr_accounted += (end - start) >> PAGE_SHIFT;
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@ -218,7 +218,6 @@ void unlink_file_vma(struct vm_area_struct *vma)
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mutex_lock(&mapping->i_mmap_mutex);
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__remove_shared_vm_struct(vma, file, mapping);
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mutex_unlock(&mapping->i_mmap_mutex);
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uprobe_munmap(vma);
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}
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}
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@ -548,10 +547,11 @@ again: remove_next = 1 + (end > next->vm_end);
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mapping = file->f_mapping;
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if (!(vma->vm_flags & VM_NONLINEAR)) {
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root = &mapping->i_mmap;
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uprobe_munmap(vma);
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uprobe_munmap(vma, vma->vm_start, vma->vm_end);
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if (adjust_next)
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uprobe_munmap(next);
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uprobe_munmap(next, next->vm_start,
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next->vm_end);
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}
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mutex_lock(&mapping->i_mmap_mutex);
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@ -632,7 +632,7 @@ again: remove_next = 1 + (end > next->vm_end);
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if (remove_next) {
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if (file) {
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uprobe_munmap(next);
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uprobe_munmap(next, next->vm_start, next->vm_end);
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fput(file);
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if (next->vm_flags & VM_EXECUTABLE)
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removed_exe_file_vma(mm);
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