mm, hugetlb: allow for "high" userspace addresses

commit 5f24d5a579d1eace79d505b148808a850b417d4c upstream.

This is a fix for commit f6795053dac8 ("mm: mmap: Allow for "high"
userspace addresses") for hugetlb.

This patch adds support for "high" userspace addresses that are
optionally supported on the system and have to be requested via a hint
mechanism ("high" addr parameter to mmap).

Architectures such as powerpc and x86 achieve this by making changes to
their architectural versions of hugetlb_get_unmapped_area() function.
However, arm64 uses the generic version of that function.

So take into account arch_get_mmap_base() and arch_get_mmap_end() in
hugetlb_get_unmapped_area().  To allow that, move those two macros out
of mm/mmap.c into include/linux/sched/mm.h

If these macros are not defined in architectural code then they default
to (TASK_SIZE) and (base) so should not introduce any behavioural
changes to architectures that do not define them.

For the time being, only ARM64 is affected by this change.

Catalin (ARM64) said
 "We should have fixed hugetlb_get_unmapped_area() as well when we added
  support for 52-bit VA. The reason for commit f6795053dac8 was to
  prevent normal mmap() from returning addresses above 48-bit by default
  as some user-space had hard assumptions about this.

  It's a slight ABI change if you do this for hugetlb_get_unmapped_area()
  but I doubt anyone would notice. It's more likely that the current
  behaviour would cause issues, so I'd rather have them consistent.

  Basically when arm64 gained support for 52-bit addresses we did not
  want user-space calling mmap() to suddenly get such high addresses,
  otherwise we could have inadvertently broken some programs (similar
  behaviour to x86 here). Hence we added commit f6795053dac8. But we
  missed hugetlbfs which could still get such high mmap() addresses. So
  in theory that's a potential regression that should have bee addressed
  at the same time as commit f6795053dac8 (and before arm64 enabled
  52-bit addresses)"

Link: https://lkml.kernel.org/r/ab847b6edb197bffdfe189e70fb4ac76bfe79e0d.1650033747.git.christophe.leroy@csgroup.eu
Fixes: f6795053dac8 ("mm: mmap: Allow for "high" userspace addresses")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Steve Capper <steve.capper@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>	[5.0.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 104061c3f1ba184bbff0332bf612225bb748975c..7d039ba5ae28b5e9d5c9278d94c1c4c5bc3fed7b 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -211,7 +211,7 @@ hugetlb_get_unmapped_area_bottomup(struct file *file, unsigned long addr,
        info.flags = 0;
        info.length = len;
        info.low_limit = current->mm->mmap_base;
-       info.high_limit = TASK_SIZE;
+       info.high_limit = arch_get_mmap_end(addr);
        info.align_mask = PAGE_MASK & ~huge_page_mask(h);
        info.align_offset = 0;
        return vm_unmapped_area(&info);
@@ -227,7 +227,7 @@ hugetlb_get_unmapped_area_topdown(struct file *file, unsigned long addr,
        info.flags = VM_UNMAPPED_AREA_TOPDOWN;
        info.length = len;
        info.low_limit = max(PAGE_SIZE, mmap_min_addr);
-       info.high_limit = current->mm->mmap_base;
+       info.high_limit = arch_get_mmap_base(addr, current->mm->mmap_base);
        info.align_mask = PAGE_MASK & ~huge_page_mask(h);
        info.align_offset = 0;
        addr = vm_unmapped_area(&info);
@@ -242,7 +242,7 @@ hugetlb_get_unmapped_area_topdown(struct file *file, unsigned long addr,
                VM_BUG_ON(addr != -ENOMEM);
                info.flags = 0;
                info.low_limit = current->mm->mmap_base;
-               info.high_limit = TASK_SIZE;
+               info.high_limit = arch_get_mmap_end(addr);
                addr = vm_unmapped_area(&info);
        }
 
@@ -256,6 +256,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        struct hstate *h = hstate_file(file);
+       const unsigned long mmap_end = arch_get_mmap_end(addr);
 
        if (len & ~huge_page_mask(h))
                return -EINVAL;
@@ -271,7 +272,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
        if (addr) {
                addr = ALIGN(addr, huge_page_size(h));
                vma = find_vma(mm, addr);
-               if (TASK_SIZE - len >= addr &&
+               if (mmap_end - len >= addr &&
                    (!vma || addr + len <= vm_start_gap(vma)))
                        return addr;
        }

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 3a1d899019af00bb2b99a15b43f2f4f5a5b11661..ab0da04ac9ee71afcb81b109244782db6984cc39 100644 (file)
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -133,6 +133,14 @@ static inline void mm_update_next_owner(struct mm_struct *mm)
 #endif /* CONFIG_MEMCG */
 
 #ifdef CONFIG_MMU
+#ifndef arch_get_mmap_end
+#define arch_get_mmap_end(addr)        (TASK_SIZE)
+#endif
+
+#ifndef arch_get_mmap_base
+#define arch_get_mmap_base(addr, base) (base)
+#endif
+
 extern void arch_pick_mmap_layout(struct mm_struct *mm,
                                  struct rlimit *rlim_stack);
 extern unsigned long

diff --git a/mm/mmap.c b/mm/mmap.c
index 58cfd5b1e0b16e157a5dd2ca011c122e171233e0..88e6863677768713e04af2b13c1f145b7d4a3118 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2077,14 +2077,6 @@ found_highest:
 }
 
 
-#ifndef arch_get_mmap_end
-#define arch_get_mmap_end(addr)        (TASK_SIZE)
-#endif
-
-#ifndef arch_get_mmap_base
-#define arch_get_mmap_base(addr, base) (base)
-#endif
-
 /* Get an address range which is currently unmapped.
  * For shmat() with addr=0.
  *