From 55e317e2091fa05cae6d6cf86db8cddf6eb58d5d Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Thu, 28 Mar 2013 16:26:23 -0700 Subject: [PATCH] Revert "mm: introduce VM_POPULATE flag to better deal with racy userspace programs" This reverts commit f699e4644003 ("mm: introduce VM_POPULATE flag to better deal with racy userspace programs"). VM_POPULATE only has any effect when userspace plays racy games with vmas by trying to unmap and remap memory regions that mmap or mlock are operating on. Also, the only effect of VM_POPULATE when userspace plays such games is that it avoids populating new memory regions that get remapped into the address range that was being operated on by the original mmap or mlock calls. Let's remove VM_POPULATE as there isn't any strong argument to mandate a new vm_flag. Signed-off-by: Michel Lespinasse Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds --- include/linux/mm.h | 1 - include/linux/mman.h | 4 +--- mm/fremap.c | 12 ++---------- mm/mlock.c | 11 +++++------ mm/mmap.c | 4 +++- 5 files changed, 11 insertions(+), 21 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 7acc9dc73c9f2..e19ff30ad0a21 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -87,7 +87,6 @@ extern unsigned int kobjsize(const void *objp); #define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */ #define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */ -#define VM_POPULATE 0x00001000 #define VM_LOCKED 0x00002000 #define VM_IO 0x00004000 /* Memory mapped I/O or similar */ diff --git a/include/linux/mman.h b/include/linux/mman.h index 61c7a87e5d2b3..9aa863da287fe 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -79,8 +79,6 @@ calc_vm_flag_bits(unsigned long flags) { return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) | _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) | - ((flags & MAP_LOCKED) ? (VM_LOCKED | VM_POPULATE) : 0) | - (((flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE) ? - VM_POPULATE : 0); + _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ); } #endif /* _LINUX_MMAN_H */ diff --git a/mm/fremap.c b/mm/fremap.c index 4723ac8d2fc20..87da3590c61e2 100644 --- a/mm/fremap.c +++ b/mm/fremap.c @@ -204,10 +204,8 @@ get_write_lock: unsigned long addr; struct file *file = get_file(vma->vm_file); - vm_flags = vma->vm_flags; - if (!(flags & MAP_NONBLOCK)) - vm_flags |= VM_POPULATE; - addr = mmap_region(file, start, size, vm_flags, pgoff); + addr = mmap_region(file, start, size, + vma->vm_flags, pgoff); fput(file); if (IS_ERR_VALUE(addr)) { err = addr; @@ -226,12 +224,6 @@ get_write_lock: mutex_unlock(&mapping->i_mmap_mutex); } - if (!(flags & MAP_NONBLOCK) && !(vma->vm_flags & VM_POPULATE)) { - if (!has_write_lock) - goto get_write_lock; - vma->vm_flags |= VM_POPULATE; - } - if (vma->vm_flags & VM_LOCKED) { /* * drop PG_Mlocked flag for over-mapped range diff --git a/mm/mlock.c b/mm/mlock.c index 1c5e33fce6391..79b7cf7d1bca7 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -358,7 +358,7 @@ static int do_mlock(unsigned long start, size_t len, int on) newflags = vma->vm_flags & ~VM_LOCKED; if (on) - newflags |= VM_LOCKED | VM_POPULATE; + newflags |= VM_LOCKED; tmp = vma->vm_end; if (tmp > end) @@ -418,8 +418,7 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) * range with the first VMA. Also, skip undesirable VMA types. */ nend = min(end, vma->vm_end); - if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_POPULATE)) != - VM_POPULATE) + if (vma->vm_flags & (VM_IO | VM_PFNMAP)) continue; if (nstart < vma->vm_start) nstart = vma->vm_start; @@ -492,9 +491,9 @@ static int do_mlockall(int flags) struct vm_area_struct * vma, * prev = NULL; if (flags & MCL_FUTURE) - current->mm->def_flags |= VM_LOCKED | VM_POPULATE; + current->mm->def_flags |= VM_LOCKED; else - current->mm->def_flags &= ~(VM_LOCKED | VM_POPULATE); + current->mm->def_flags &= ~VM_LOCKED; if (flags == MCL_FUTURE) goto out; @@ -503,7 +502,7 @@ static int do_mlockall(int flags) newflags = vma->vm_flags & ~VM_LOCKED; if (flags & MCL_CURRENT) - newflags |= VM_LOCKED | VM_POPULATE; + newflags |= VM_LOCKED; /* Ignore errors */ mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags); diff --git a/mm/mmap.c b/mm/mmap.c index 2664a47cec937..6466699b16cbc 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1306,7 +1306,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, } addr = mmap_region(file, addr, len, vm_flags, pgoff); - if (!IS_ERR_VALUE(addr) && (vm_flags & VM_POPULATE)) + if (!IS_ERR_VALUE(addr) && + ((vm_flags & VM_LOCKED) || + (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE)) *populate = len; return addr; } -- 2.39.5