Incorrect invocation of VMA callbacks when the VMA is no longer in a
consistent state is bug prone and risky to perform.
With regards to the important vm_ops->close() callback We have gone to
great lengths to try to track whether or not we ought to close VMAs.
Rather than doing so and risking making a mistake somewhere, instead
unconditionally close and reset vma->vm_ops to an empty dummy operations
set with a NULL .close operator.
We introduce a new function to do so - vma_close() - and simplify existing
vms logic which tracked whether we needed to close or not.
This simplifies the logic, avoids incorrect double-calling of the .close()
callback and allows us to update error paths to simply call vma_close()
unconditionally - making VMA closure idempotent.
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Cc: stable <stable@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Reviewed-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
mm/internal.h | 18 ++++++++++++++++++
mm/mmap.c | 5 ++---
mm/nommu.c | 3 +--
mm/vma.c | 14 +++++---------
mm/vma.h | 4 +---
5 files changed, 27 insertions(+), 17 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index af032e76dfd4..0c4bf09bf788 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -135,6 +135,24 @@ static inline int mmap_file(struct file *file, struct vm_area_struct *vma)
return err;
}
+/*
+ * If the VMA has a close hook then close it, and since closing it might leave
+ * it in an inconsistent state which makes the use of any hooks suspect, clear
+ * them down by installing dummy empty hooks.
+ */
+static inline void vma_close(struct vm_area_struct *vma)
+{
+ if (vma->vm_ops && vma->vm_ops->close) {
+ vma->vm_ops->close(vma);
+
+ /*
+ * The mapping is in an inconsistent state, and no further hooks
+ * may be invoked upon it.
+ */
+ vma->vm_ops = &vma_dummy_vm_ops;
+ }
+}
+
#ifdef CONFIG_MMU
/* Flags for folio_pte_batch(). */
diff --git a/mm/mmap.c b/mm/mmap.c
index 10f4ccaf491b..d55c58e99a54 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1576,8 +1576,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
return addr;
close_and_free_vma:
- if (file && !vms.closed_vm_ops && vma->vm_ops && vma->vm_ops->close)
- vma->vm_ops->close(vma);
+ vma_close(vma);
if (file || vma->vm_file) {
unmap_and_free_vma:
@@ -1937,7 +1936,7 @@ void exit_mmap(struct mm_struct *mm)
do {
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += vma_pages(vma);
- remove_vma(vma, /* unreachable = */ true, /* closed = */ false);
+ remove_vma(vma, /* unreachable = */ true);
count++;
cond_resched();
vma = vma_next(&vmi);
diff --git a/mm/nommu.c b/mm/nommu.c
index f9ccc02458ec..635d028d647b 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -589,8 +589,7 @@ static int delete_vma_from_mm(struct vm_area_struct *vma)
*/
static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
{
- if (vma->vm_ops && vma->vm_ops->close)
- vma->vm_ops->close(vma);
+ vma_close(vma);
if (vma->vm_file)
fput(vma->vm_file);
put_nommu_region(vma->vm_region);
diff --git a/mm/vma.c b/mm/vma.c
index 3c5a80876725..bb7cfa2dc282 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -323,11 +323,10 @@ static bool can_vma_merge_right(struct vma_merge_struct *vmg,
/*
* Close a vm structure and free it.
*/
-void remove_vma(struct vm_area_struct *vma, bool unreachable, bool closed)
+void remove_vma(struct vm_area_struct *vma, bool unreachable)
{
might_sleep();
- if (!closed && vma->vm_ops && vma->vm_ops->close)
- vma->vm_ops->close(vma);
+ vma_close(vma);
if (vma->vm_file)
fput(vma->vm_file);
mpol_put(vma_policy(vma));
@@ -1115,9 +1114,7 @@ void vms_clean_up_area(struct vma_munmap_struct *vms,
vms_clear_ptes(vms, mas_detach, true);
mas_set(mas_detach, 0);
mas_for_each(mas_detach, vma, ULONG_MAX)
- if (vma->vm_ops && vma->vm_ops->close)
- vma->vm_ops->close(vma);
- vms->closed_vm_ops = true;
+ vma_close(vma);
}
/*
@@ -1160,7 +1157,7 @@ void vms_complete_munmap_vmas(struct vma_munmap_struct *vms,
/* Remove and clean up vmas */
mas_set(mas_detach, 0);
mas_for_each(mas_detach, vma, ULONG_MAX)
- remove_vma(vma, /* = */ false, vms->closed_vm_ops);
+ remove_vma(vma, /* unreachable = */ false);
vm_unacct_memory(vms->nr_accounted);
validate_mm(mm);
@@ -1684,8 +1681,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
return new_vma;
out_vma_link:
- if (new_vma->vm_ops && new_vma->vm_ops->close)
- new_vma->vm_ops->close(new_vma);
+ vma_close(new_vma);
if (new_vma->vm_file)
fput(new_vma->vm_file);
diff --git a/mm/vma.h b/mm/vma.h
index 55457cb68200..75558b5e9c8c 100644
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -42,7 +42,6 @@ struct vma_munmap_struct {
int vma_count; /* Number of vmas that will be removed */
bool unlock; /* Unlock after the munmap */
bool clear_ptes; /* If there are outstanding PTE to be cleared */
- bool closed_vm_ops; /* call_mmap() was encountered, so vmas may be closed */
/* 1 byte hole */
unsigned long nr_pages; /* Number of pages being removed */
unsigned long locked_vm; /* Number of locked pages */
@@ -198,7 +197,6 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms,
vms->unmap_start = FIRST_USER_ADDRESS;
vms->unmap_end = USER_PGTABLES_CEILING;
vms->clear_ptes = false;
- vms->closed_vm_ops = false;
}
#endif
@@ -269,7 +267,7 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
unsigned long start, size_t len, struct list_head *uf,
bool unlock);
-void remove_vma(struct vm_area_struct *vma, bool unreachable, bool closed);
+void remove_vma(struct vm_area_struct *vma, bool unreachable);
void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
struct vm_area_struct *prev, struct vm_area_struct *next);
--
2.47.0
