Currently each xol_area has its own instance of vm_special_mapping, this
is suboptimal and ugly. Kill xol_area->xol_mapping and add a single global
instance of vm_special_mapping, the ->fault() method can use area->pages
rather than xol_mapping->pages.
As a side effect this fixes the problem introduced by the recent commit
223febc6e557 ("mm: add optional close() to struct vm_special_mapping"), if
special_mapping_close() is called from the __mmput() paths, it will use
vma->vm_private_data = &area->xol_mapping freed by uprobe_clear_state().
Reported-by: Sven Schnelle <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 223febc6e557 ("mm: add optional close() to struct vm_special_mapping")
Signed-off-by: Oleg Nesterov <[email protected]>
---
kernel/events/uprobes.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 73cc47708679..a478e028043f 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -99,7 +99,6 @@ struct xol_area {
atomic_t slot_count; /* number of in-use
slots */
unsigned long *bitmap; /* 0 = free slot */
- struct vm_special_mapping xol_mapping;
struct page *pages[2];
/*
* We keep the vma's vm_start rather than a pointer to the vma
@@ -1433,6 +1432,21 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned
long start, unsigned lon
set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
}
+static vm_fault_t xol_fault(const struct vm_special_mapping *sm,
+ struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+ struct xol_area *area = vma->vm_mm->uprobes_state.xol_area;
+
+ vmf->page = area->pages[0];
+ get_page(vmf->page);
+ return 0;
+}
+
+static const struct vm_special_mapping xol_mapping = {
+ .name = "[uprobes]",
+ .fault = xol_fault,
+};
+
/* Slot allocation for XOL */
static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
{
@@ -1459,7 +1473,7 @@ static int xol_add_vma(struct mm_struct *mm, struct
xol_area *area)
vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
- &area->xol_mapping);
+ &xol_mapping);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto fail;
@@ -1498,9 +1512,6 @@ static struct xol_area *__create_xol_area(unsigned long
vaddr)
if (!area->bitmap)
goto free_area;
- area->xol_mapping.name = "[uprobes]";
- area->xol_mapping.fault = NULL;
- area->xol_mapping.pages = area->pages;
area->pages[0] = alloc_page(GFP_HIGHUSER);
if (!area->pages[0])
goto free_bitmap;
--
2.25.1.362.g51ebf55
