[PATCH v9 1/3] mm: untag user pointers in mmap/munmap/mremap/brk

Catalin Marinas
2019-08-21T16:47:45Z

There isn't a good reason to differentiate between the user address
space layout modification syscalls and the other memory
permission/attributes ones (e.g. mprotect, madvise) w.r.t. the tagged
address ABI. Untag the user addresses on entry to these functions.

Acked-by: Will Deacon <will@kernel.org>
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
mm/mmap.c | 5 +++++
mm/mremap.c | 6 +-----
2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 7e8c3e8ae75f..b766b633b7ae 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -201,6 +201,8 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
bool downgraded = false;
LIST_HEAD(uf);

+ brk = untagged_addr(brk);
+
if (down_write_killable(&mm->mmap_sem))
return -EINTR;

@@ -1573,6 +1575,8 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
struct file *file = NULL;
unsigned long retval;

+ addr = untagged_addr(addr);
+
if (!(flags & MAP_ANONYMOUS)) {
audit_mmap_fd(fd, flags);
file = fget(fd);
@@ -2874,6 +2878,7 @@ EXPORT_SYMBOL(vm_munmap);

SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
{
+ addr = untagged_addr(addr);
profile_munmap(addr);
return __vm_munmap(addr, len, true);
}
diff --git a/mm/mremap.c b/mm/mremap.c
index 64c9a3b8be0a..1fc8a29fbe3f 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -606,12 +606,8 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
LIST_HEAD(uf_unmap_early);
LIST_HEAD(uf_unmap);

- /*
- * Architectures may interpret the tag passed to mmap as a background
- * colour for the corresponding vma. For mremap we don't allow tagged
- * new_addr to preserve similar behaviour to mmap.
- */
addr = untagged_addr(addr);
+ new_addr = untagged_addr(new_addr);

if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
return ret;