The patch titled
Subject: mm: unconditionally close VMAs on error
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-unconditionally-close-vmas-on-error.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-unconditionally-close-vmas-on-error.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Subject: mm: unconditionally close VMAs on error
Date: Wed, 23 Oct 2024 21:38:27 +0100
Incorrect invokation 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.
Link: https://lkml.kernel.org/r/72a81a6fb997508db644313a5fdf4d239f620da6.1729715266.git.lorenzo.stoakes@xxxxxxxxxx
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Reviewed-by: Jann Horn <jannh@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/mm/internal.h~mm-unconditionally-close-vmas-on-error
+++ a/mm/internal.h
@@ -135,6 +135,24 @@ static inline int mmap_file(struct file
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(). */
--- a/mm/mmap.c~mm-unconditionally-close-vmas-on-error
+++ a/mm/mmap.c
@@ -1572,8 +1572,7 @@ expanded:
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:
@@ -1933,7 +1932,7 @@ 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);
--- a/mm/nommu.c~mm-unconditionally-close-vmas-on-error
+++ a/mm/nommu.c
@@ -589,8 +589,7 @@ static int delete_vma_from_mm(struct vm_
*/
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);
--- a/mm/vma.c~mm-unconditionally-close-vmas-on-error
+++ a/mm/vma.c
@@ -323,11 +323,10 @@ static bool can_vma_merge_right(struct v
/*
* 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
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
/* 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 v
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);
--- a/mm/vma.h~mm-unconditionally-close-vmas-on-error
+++ a/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(struc
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 *v
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);
_
Patches currently in -mm which might be from lorenzo.stoakes@xxxxxxxxxx are
fork-do-not-invoke-uffd-on-fork-if-error-occurs.patch
fork-only-invoke-khugepaged-ksm-hooks-if-no-error.patch
mm-vma-add-expand-only-vma-merge-mode-and-optimise-do_brk_flags.patch
tools-testing-add-expand-only-mode-vma-test.patch
mm-avoid-unsafe-vma-hook-invocation-when-error-arises-on-mmap-hook.patch
mm-unconditionally-close-vmas-on-error.patch
mm-refactor-map_deny_write_exec.patch
mm-resolve-faulty-mmap_region-error-path-behaviour.patch
tools-testing-add-additional-vma_internalh-stubs.patch
mm-isolate-mmap-internal-logic-to-mm-vmac.patch
mm-refactor-__mmap_region.patch
mm-defer-second-attempt-at-merge-on-mmap.patch
selftests-mm-add-pkey_sighandler_xx-hugetlb_dio-to-gitignore.patch
mm-refactor-mm_access-to-not-return-null.patch
mm-refactor-mm_access-to-not-return-null-fix.patch
mm-madvise-unrestrict-process_madvise-for-current-process.patch
maple_tree-do-not-hash-pointers-on-dump-in-debug-mode.patch
tools-testing-fix-phys_addr_t-size-on-64-bit-systems.patch
