From: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Uprobes has a hook(uprobe_munmap) in unmap path to keep the uprobes count
sane. In the exit path this hook gets called in unlink_file_vma. However by
the time unlink_file_vma is called, the pages would have been unmapped
(unmap_vmas) and the rss_stat counts accounted (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 filebacked page being reread by uprobe_munmap and hence
it does not find the breakpoint.
This patch fixes this problem by moving the hook 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 commit c3f0327f8e9d7.
Signed-off-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
---
include/linux/uprobes.h | 5 +++--
kernel/events/uprobes.c | 4 ++--
mm/memory.c | 3 +++
mm/mmap.c | 8 ++++----
4 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index d594d3b..efe4b33 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -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)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c5caeec..985be4d 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -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.
diff --git a/mm/memory.c b/mm/memory.c
index 6105f47..bf8b403 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -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;
diff --git a/mm/mmap.c b/mm/mmap.c
index b17a39f..15c21a1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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);
--
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