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authorCatalin Marinas <catalin.marinas@arm.com>2020-02-19 12:31:56 +0000
committerWill Deacon <will@kernel.org>2020-02-20 10:03:14 +0000
commitdcde237319e626d1ec3c9d8b7613032f0fd4663a (patch)
treefba292b1a70328443aa982471c65a28c2ea28572 /mm
parentce4a64e1f656138e2a1481049ea554720f86b43a (diff)
mm: Avoid creating virtual address aliases in brk()/mmap()/mremap()
Currently the arm64 kernel ignores the top address byte passed to brk(), mmap() and mremap(). When the user is not aware of the 56-bit address limit or relies on the kernel to return an error, untagging such pointers has the potential to create address aliases in user-space. Passing a tagged address to munmap(), madvise() is permitted since the tagged pointer is expected to be inside an existing mapping. The current behaviour breaks the existing glibc malloc() implementation which relies on brk() with an address beyond 56-bit to be rejected by the kernel. Remove untagging in the above functions by partially reverting commit ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk"). In addition, update the arm64 tagged-address-abi.rst document accordingly. Link: https://bugzilla.redhat.com/1797052 Fixes: ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk") Cc: <stable@vger.kernel.org> # 5.4.x- Cc: Florian Weimer <fweimer@redhat.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Reported-by: Victor Stinner <vstinner@redhat.com> Acked-by: Will Deacon <will@kernel.org> Acked-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c4
-rw-r--r--mm/mremap.c1
2 files changed, 0 insertions, 5 deletions
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;