mm, hugetlb: allow for "high" userspace addresses

BugLink: https://bugs.launchpad.net/bugs/1972905
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 54c4e0b0dda4a2cc5d2951211290387381e6df44..bb0651a4a12870659019dba217ca825886148bd1 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -206,7 +206,7 @@ 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);
@@ -222,7 +222,7 @@ 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);
@@ -237,7 +237,7 @@ 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);
        }
 
@@ -251,6 +251,7 @@ 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;
@@ -266,7 +267,7 @@ 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 5561486fddef7a31675958319a240a9369e2bdd7..95fb7aaaec8de049c5d5e340b08bb216df290c70 100644 (file)
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -106,6 +106,14 @@ 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 9c5edf652125bb738f00f952e409b5f230d4ce6d..5920b2d6103232348c2a70c6805405b263b8bebd 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2113,14 +2113,6 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
        return addr;
 }
 
-#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.
  *