diff options
Diffstat (limited to '0001-mm-Avoid-creating-virtual-address-aliases-in-brk-mma.patch')
| -rw-r--r-- | 0001-mm-Avoid-creating-virtual-address-aliases-in-brk-mma.patch | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/0001-mm-Avoid-creating-virtual-address-aliases-in-brk-mma.patch b/0001-mm-Avoid-creating-virtual-address-aliases-in-brk-mma.patch new file mode 100644 index 000000000..6f3bd3c72 --- /dev/null +++ b/0001-mm-Avoid-creating-virtual-address-aliases-in-brk-mma.patch @@ -0,0 +1,95 @@ +From a34309d16f41c48ffd90e56a6f865d6a1a8c49f0 Mon Sep 17 00:00:00 2001 +From: Catalin Marinas <catalin.marinas@arm.com> +Date: Wed, 19 Feb 2020 12:31:56 +0000 +Subject: [PATCH] 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: Andrew Morton <akpm@linux-foundation.org> +Cc: Florian Weimer <fweimer@redhat.com> +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> +--- + Documentation/arm64/tagged-address-abi.rst | 11 +++++++++-- + mm/mmap.c | 4 ---- + mm/mremap.c | 1 - + 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..f6289116893c 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 of aliasing 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 4390dbea4aa5..514cc19c5916 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; + +@@ -1583,8 +1581,6 @@ 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 1fc8a29fbe3f..1d98281f7204 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; +-- +2.24.1 + |