[PATCH v1 5/7] mm: remove VM_DENYWRITE

David Hildenbrand
2021-08-12T08:46:03Z

All in-tree users of MAP_DENYWRITE are gone. MAP_DENYWRITE cannot be
set from user space, so all users are gone; let's remove it.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
fs/proc/task_mmu.c | 1 -
include/linux/mm.h | 1 -
include/linux/mman.h | 1 -
include/trace/events/mmflags.h | 1 -
kernel/events/core.c | 2 --
kernel/fork.c | 3 ---
lib/test_printf.c | 5 ++---
mm/mmap.c | 27 +++------------------------
8 files changed, 5 insertions(+), 36 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index eb97468dfe4c..cf25be3e0321 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -619,7 +619,6 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
[ilog2(VM_MAYSHARE)] = "ms",
[ilog2(VM_GROWSDOWN)] = "gd",
[ilog2(VM_PFNMAP)] = "pf",
- [ilog2(VM_DENYWRITE)] = "dw",
[ilog2(VM_LOCKED)] = "lo",
[ilog2(VM_IO)] = "io",
[ilog2(VM_SEQ_READ)] = "sr",
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 197505324b74..434cc97ddcf8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -281,7 +281,6 @@ extern unsigned int kobjsize(const void *objp);
#define VM_GROWSDOWN 0x00000100 /* general info on the segment */
#define VM_UFFD_MISSING 0x00000200 /* missing pages tracking */
#define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
-#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */
#define VM_UFFD_WP 0x00001000 /* wrprotect pages tracking */

#define VM_LOCKED 0x00002000
diff --git a/include/linux/mman.h b/include/linux/mman.h
index ebb09a964272..bd9aadda047b 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -153,7 +153,6 @@ static inline unsigned long
calc_vm_flag_bits(unsigned long flags)
{
return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
- _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) |
_calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) |
_calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) |
arch_calc_vm_flag_bits(flags);
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 390270e00a1d..f44c3fb8da1a 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -163,7 +163,6 @@ IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
{VM_UFFD_MISSING, "uffd_missing" }, \
IF_HAVE_UFFD_MINOR(VM_UFFD_MINOR, "uffd_minor" ) \
{VM_PFNMAP, "pfnmap" }, \
- {VM_DENYWRITE, "denywrite" }, \
{VM_UFFD_WP, "uffd_wp" }, \
{VM_LOCKED, "locked" }, \
{VM_IO, "io" }, \
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1cb1f9b8392e..19767bb9933c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8307,8 +8307,6 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
else
flags = MAP_PRIVATE;

- if (vma->vm_flags & VM_DENYWRITE)
- flags |= MAP_DENYWRITE;
if (vma->vm_flags & VM_LOCKED)
flags |= MAP_LOCKED;
if (is_vm_hugetlb_page(vma))
diff --git a/kernel/fork.c b/kernel/fork.c
index 5d904878f19b..31df30d9f1a9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -560,12 +560,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
file = tmp->vm_file;
if (file) {
- struct inode *inode = file_inode(file);
struct address_space *mapping = file->f_mapping;

get_file(file);
- if (tmp->vm_flags & VM_DENYWRITE)
- put_write_access(inode);
i_mmap_lock_write(mapping);
if (tmp->vm_flags & VM_SHARED)
mapping_allow_writable(mapping);
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 8ac71aee46af..8a48b61c3763 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -675,9 +675,8 @@ flags(void)
"uptodate|dirty|lru|active|swapbacked",
cmp_buffer);

- flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC
- | VM_DENYWRITE;
- test("read|exec|mayread|maywrite|mayexec|denywrite", "%pGv", &flags);
+ flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+ test("read|exec|mayread|maywrite|mayexec", "%pGv", &flags);

gfp = GFP_TRANSHUGE;
test("GFP_TRANSHUGE", "%pGg", &gfp);
diff --git a/mm/mmap.c b/mm/mmap.c
index ca54d36d203a..589dc1dc13db 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -148,8 +148,6 @@ void vma_set_page_prot(struct vm_area_struct *vma)
static void __remove_shared_vm_struct(struct vm_area_struct *vma,
struct file *file, struct address_space *mapping)
{
- if (vma->vm_flags & VM_DENYWRITE)
- allow_write_access(file);
if (vma->vm_flags & VM_SHARED)
mapping_unmap_writable(mapping);

@@ -666,8 +664,6 @@ static void __vma_link_file(struct vm_area_struct *vma)
if (file) {
struct address_space *mapping = file->f_mapping;

- if (vma->vm_flags & VM_DENYWRITE)
- put_write_access(file_inode(file));
if (vma->vm_flags & VM_SHARED)
mapping_allow_writable(mapping);

@@ -1788,22 +1784,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vma->vm_pgoff = pgoff;

if (file) {
- if (vm_flags & VM_DENYWRITE) {
- error = deny_write_access(file);
- if (error)
- goto free_vma;
- }
if (vm_flags & VM_SHARED) {
error = mapping_map_writable(file->f_mapping);
if (error)
- goto allow_write_and_free_vma;
+ goto free_vma;
}

- /* ->mmap() can change vma->vm_file, but must guarantee that
- * vma_link() below can deny write-access if VM_DENYWRITE is set
- * and map writably if VM_SHARED is set. This usually means the
- * new file must not have been exposed to user-space, yet.
- */
vma->vm_file = get_file(file);
error = call_mmap(file, vma);
if (error)
@@ -1860,13 +1846,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,

vma_link(mm, vma, prev, rb_link, rb_parent);
/* Once vma denies write, undo our temporary denial count */
- if (file) {
unmap_writable:
- if (vm_flags & VM_SHARED)
- mapping_unmap_writable(file->f_mapping);
- if (vm_flags & VM_DENYWRITE)
- allow_write_access(file);
- }
+ if (file && vm_flags & VM_SHARED)
+ mapping_unmap_writable(file->f_mapping);
file = vma->vm_file;
out:
perf_event_mmap(vma);
@@ -1906,9 +1888,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
charged = 0;
if (vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
-allow_write_and_free_vma:
- if (vm_flags & VM_DENYWRITE)
- allow_write_access(file);
free_vma:
vm_area_free(vma);
unacct_error:
--
2.31.1