From: Peter Collingbourne pcc@google.com
stable inclusion from stable-5.10.54 commit 0b591c020d280cc0cd92d84c24a5be89b4c57033 bugzilla: 175586 https://gitee.com/openeuler/kernel/issues/I4DVDU
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit e71e2ace5721a8b921dca18b045069e7bb411277 upstream.
Patch series "userfaultfd: do not untag user pointers", v5.
If a user program uses userfaultfd on ranges of heap memory, it may end up passing a tagged pointer to the kernel in the range.start field of the UFFDIO_REGISTER ioctl. This can happen when using an MTE-capable allocator, or on Android if using the Tagged Pointers feature for MTE readiness [1].
When a fault subsequently occurs, the tag is stripped from the fault address returned to the application in the fault.address field of struct uffd_msg. However, from the application's perspective, the tagged address *is* the memory address, so if the application is unaware of memory tags, it may get confused by receiving an address that is, from its point of view, outside of the bounds of the allocation. We observed this behavior in the kselftest for userfaultfd [2] but other applications could have the same problem.
Address this by not untagging pointers passed to the userfaultfd ioctls. Instead, let the system call fail. Also change the kselftest to use mmap so that it doesn't encounter this problem.
[1] https://source.android.com/devices/tech/debug/tagged-pointers [2] tools/testing/selftests/vm/userfaultfd.c
This patch (of 2):
Do not untag pointers passed to the userfaultfd ioctls. Instead, let the system call fail. This will provide an early indication of problems with tag-unaware userspace code instead of letting the code get confused later, and is consistent with how we decided to handle brk/mmap/mremap in commit dcde237319e6 ("mm: Avoid creating virtual address aliases in brk()/mmap()/mremap()"), as well as being consistent with the existing tagged address ABI documentation relating to how ioctl arguments are handled.
The code change is a revert of commit 7d0325749a6c ("userfaultfd: untag user pointers") plus some fixups to some additional calls to validate_range that have appeared since then.
[1] https://source.android.com/devices/tech/debug/tagged-pointers [2] tools/testing/selftests/vm/userfaultfd.c
Link: https://lkml.kernel.org/r/20210714195437.118982-1-pcc@google.com Link: https://lkml.kernel.org/r/20210714195437.118982-2-pcc@google.com Link: https://linux-review.googlesource.com/id/I761aa9f0344454c482b83fcfcce547db0a... Fixes: 63f0c6037965 ("arm64: Introduce prctl() options to control the tagged user addresses ABI") Signed-off-by: Peter Collingbourne pcc@google.com Reviewed-by: Andrey Konovalov andreyknvl@gmail.com Reviewed-by: Catalin Marinas catalin.marinas@arm.com Cc: Alistair Delva adelva@google.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Dave Martin Dave.Martin@arm.com Cc: Evgenii Stepanov eugenis@google.com Cc: Lokesh Gidra lokeshgidra@google.com Cc: Mitch Phillips mitchp@google.com Cc: Vincenzo Frascino vincenzo.frascino@arm.com Cc: Will Deacon will@kernel.org Cc: William McVicker willmcvicker@google.com Cc: stable@vger.kernel.org [5.4] 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: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com Signed-off-by: Chen Jun chenjun102@huawei.com --- Documentation/arm64/tagged-address-abi.rst | 26 +++++++++++++++------- fs/userfaultfd.c | 24 +++++++++----------- 2 files changed, 29 insertions(+), 21 deletions(-)
diff --git a/Documentation/arm64/tagged-address-abi.rst b/Documentation/arm64/tagged-address-abi.rst index 4a9d9c794ee5..7d255249094d 100644 --- a/Documentation/arm64/tagged-address-abi.rst +++ b/Documentation/arm64/tagged-address-abi.rst @@ -45,14 +45,24 @@ 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. ``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. + tagged pointers in this context is allowed with these exceptions: + + - ``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. + + - The ``range.start``, ``start`` and ``dst`` arguments to the + ``UFFDIO_*`` ``ioctl()``s used on a file descriptor obtained from + ``userfaultfd()``, as fault addresses subsequently obtained by reading + the file descriptor will be untagged, which may otherwise confuse + tag-unaware programs. + + NOTE: This behaviour changed in v5.14 and so some earlier kernels may + incorrectly accept valid tagged pointers for this system call.
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/fs/userfaultfd.c b/fs/userfaultfd.c index bd71fbd68199..6a1d53f62d5a 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1240,23 +1240,21 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, }
static __always_inline int validate_range(struct mm_struct *mm, - __u64 *start, __u64 len) + __u64 start, __u64 len) { __u64 task_size = mm->task_size;
- *start = untagged_addr(*start); - - if (*start & ~PAGE_MASK) + if (start & ~PAGE_MASK) return -EINVAL; if (len & ~PAGE_MASK) return -EINVAL; if (!len) return -EINVAL; - if (*start < mmap_min_addr) + if (start < mmap_min_addr) return -EINVAL; - if (*start >= task_size) + if (start >= task_size) return -EINVAL; - if (len > task_size - *start) + if (len > task_size - start) return -EINVAL; return 0; } @@ -1324,7 +1322,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) vm_flags |= VM_UFFD_WP;
- ret = validate_range(mm, &uffdio_register.range.start, + ret = validate_range(mm, uffdio_register.range.start, uffdio_register.range.len); if (ret) goto out; @@ -1524,7 +1522,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) goto out;
- ret = validate_range(mm, &uffdio_unregister.start, + ret = validate_range(mm, uffdio_unregister.start, uffdio_unregister.len); if (ret) goto out; @@ -1673,7 +1671,7 @@ static int userfaultfd_wake(struct userfaultfd_ctx *ctx, if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) goto out;
- ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len); + ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); if (ret) goto out;
@@ -1713,7 +1711,7 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx, sizeof(uffdio_copy)-sizeof(__s64))) goto out;
- ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len); + ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); if (ret) goto out; /* @@ -1770,7 +1768,7 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, sizeof(uffdio_zeropage)-sizeof(__s64))) goto out;
- ret = validate_range(ctx->mm, &uffdio_zeropage.range.start, + ret = validate_range(ctx->mm, uffdio_zeropage.range.start, uffdio_zeropage.range.len); if (ret) goto out; @@ -1820,7 +1818,7 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, sizeof(struct uffdio_writeprotect))) return -EFAULT;
- ret = validate_range(ctx->mm, &uffdio_wp.range.start, + ret = validate_range(ctx->mm, uffdio_wp.range.start, uffdio_wp.range.len); if (ret) return ret;