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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:
Srikar Dronamraju 2012-04-11 16:05:27 +05:30 committed by Ingo Molnar
parent 7396fa818d
commit cbc91f71b5
4 changed files with 12 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/uprobes.h
View File

@ -107,7 +107,7 @@ extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern int uprobe_mmap(struct vm_area_struct *vma);
extern void uprobe_munmap(struct vm_area_struct *vma);
extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
extern void uprobe_free_utask(struct task_struct *t);
extern void uprobe_copy_process(struct task_struct *t);
extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
@ -134,7 +134,8 @@ static inline int uprobe_mmap(struct vm_area_struct *vma)
{
return 0;
}
static inline void uprobe_munmap(struct vm_area_struct *vma)
static inline void
uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
}
static inline void uprobe_notify_resume(struct pt_regs *regs)

4
kernel/events/uprobes.c
View File

@ -1112,7 +1112,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
/*
* Called in context of a munmap of a vma.
*/
void uprobe_munmap(struct vm_area_struct *vma)
void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
struct list_head tmp_list;
struct uprobe *uprobe, *u;
@ -1138,7 +1138,7 @@ void uprobe_munmap(struct vm_area_struct *vma)
list_del(&uprobe->pending_list);
vaddr = vma_address(vma, uprobe->offset);
if (vaddr >= vma->vm_start && vaddr < vma->vm_end) {
if (vaddr >= start && vaddr < end) {
/*
* An unregister could have removed the probe before
* unmap. So check before we decrement the count.

3
mm/memory.c
View File

@ -1307,6 +1307,9 @@ static void unmap_single_vma(struct mmu_gather *tlb,
if (end <= vma->vm_start)
return;
if (vma->vm_file)
uprobe_munmap(vma, start, end);
if (vma->vm_flags & VM_ACCOUNT)
*nr_accounted += (end - start) >> PAGE_SHIFT;

8
mm/mmap.c
View File

@ -218,7 +218,6 @@ void unlink_file_vma(struct vm_area_struct *vma)
mutex_lock(&mapping->i_mmap_mutex);
__remove_shared_vm_struct(vma, file, mapping);
mutex_unlock(&mapping->i_mmap_mutex);
uprobe_munmap(vma);
}
}
@ -548,10 +547,11 @@ again: remove_next = 1 + (end > next->vm_end);
mapping = file->f_mapping;
if (!(vma->vm_flags & VM_NONLINEAR)) {
root = &mapping->i_mmap;
uprobe_munmap(vma);
uprobe_munmap(vma, vma->vm_start, vma->vm_end);
if (adjust_next)
uprobe_munmap(next);
uprobe_munmap(next, next->vm_start,
next->vm_end);
}
mutex_lock(&mapping->i_mmap_mutex);
@ -632,7 +632,7 @@ again: remove_next = 1 + (end > next->vm_end);
if (remove_next) {
if (file) {
uprobe_munmap(next);
uprobe_munmap(next, next->vm_start, next->vm_end);
fput(file);
if (next->vm_flags & VM_EXECUTABLE)
removed_exe_file_vma(mm);