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From:   David Hildenbrand <david@redhat.com>
To:     linux-kernel@vger.kernel.org
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Subject: [PATCH v2 5/7] mm: remove VM_DENYWRITE
Date:   Mon, 16 Aug 2021 21:48:38 +0200
Message-Id: <20210816194840.42769-6-david@redhat.com>
In-Reply-To: <20210816194840.42769-1-david@redhat.com>
References: <20210816194840.42769-1-david@redhat.com>
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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.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
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 56b1cd41db61..257995f62e83 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 543541764865..34d21642c44f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -570,12 +570,9 @@ 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