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-rw-r--r--Documentation/arm64/tagged-address-abi.rst11
-rw-r--r--mm/mmap.c4
-rw-r--r--mm/mremap.c1
3 files changed, 9 insertions, 7 deletions
diff --git a/Documentation/arm64/tagged-address-abi.rst b/Documentation/arm64/tagged-address-abi.rst
index d4a85d535bf9..4a9d9c794ee5 100644
--- a/Documentation/arm64/tagged-address-abi.rst
+++ b/Documentation/arm64/tagged-address-abi.rst
@@ -44,8 +44,15 @@ The AArch64 Tagged Address ABI has two stages of relaxation depending
how the user addresses are used by the kernel:
1. User addresses not accessed by the kernel but used for address space
- management (e.g. ``mmap()``, ``mprotect()``, ``madvise()``). The use
- of valid tagged pointers in this context is always allowed.
+ management (e.g. ``mprotect()``, ``madvise()``). The use of valid
+ tagged pointers in this context is allowed with the exception of
+ ``brk()``, ``mmap()`` and the ``new_address`` argument to
+ ``mremap()`` as these have the potential to alias with existing
+ user addresses.
+
+ NOTE: This behaviour changed in v5.6 and so some earlier kernels may
+ incorrectly accept valid tagged pointers for the ``brk()``,
+ ``mmap()`` and ``mremap()`` system calls.
2. User addresses accessed by the kernel (e.g. ``write()``). This ABI
relaxation is disabled by default and the application thread needs to
diff --git a/mm/mmap.c b/mm/mmap.c
index 6756b8bb0033..d681a20eb4ea 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -195,8 +195,6 @@ 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;
@@ -1557,8 +1555,6 @@ 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);
diff --git a/mm/mremap.c b/mm/mremap.c
index 122938dcec15..af363063ea23 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -607,7 +607,6 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
LIST_HEAD(uf_unmap);
addr = untagged_addr(addr);
- new_addr = untagged_addr(new_addr);
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
return ret;