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author | Jann Horn <jannh@google.com> | 2020-04-21 03:14:11 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-21 20:11:56 +0200 |
commit | bdebd6a2831b6fab69eb85cee74a8ba77f1a1cc2 (patch) | |
tree | ab0d5cf962ae15406f5784f4c3da6618ca49cfd0 /mm/vmalloc.c | |
parent | mm/shmem: fix build without THP (diff) | |
download | linux-bdebd6a2831b6fab69eb85cee74a8ba77f1a1cc2.tar.xz linux-bdebd6a2831b6fab69eb85cee74a8ba77f1a1cc2.zip |
vmalloc: fix remap_vmalloc_range() bounds checks
remap_vmalloc_range() has had various issues with the bounds checks it
promises to perform ("This function checks that addr is a valid
vmalloc'ed area, and that it is big enough to cover the vma") over time,
e.g.:
- not detecting pgoff<<PAGE_SHIFT overflow
- not detecting (pgoff<<PAGE_SHIFT)+usize overflow
- not checking whether addr and addr+(pgoff<<PAGE_SHIFT) are the same
vmalloc allocation
- comparing a potentially wildly out-of-bounds pointer with the end of
the vmalloc region
In particular, since commit fc9702273e2e ("bpf: Add mmap() support for
BPF_MAP_TYPE_ARRAY"), unprivileged users can cause kernel null pointer
dereferences by calling mmap() on a BPF map with a size that is bigger
than the distance from the start of the BPF map to the end of the
address space.
This could theoretically be used as a kernel ASLR bypass, by using
whether mmap() with a given offset oopses or returns an error code to
perform a binary search over the possible address range.
To allow remap_vmalloc_range_partial() to verify that addr and
addr+(pgoff<<PAGE_SHIFT) are in the same vmalloc region, pass the offset
to remap_vmalloc_range_partial() instead of adding it to the pointer in
remap_vmalloc_range().
In remap_vmalloc_range_partial(), fix the check against
get_vm_area_size() by using size comparisons instead of pointer
comparisons, and add checks for pgoff.
Fixes: 833423143c3a ("[PATCH] mm: introduce remap_vmalloc_range()")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@chromium.org>
Link: http://lkml.kernel.org/r/20200415222312.236431-1-jannh@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
-rw-r--r-- | mm/vmalloc.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 399f219544f7..9a8227afa073 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -34,6 +34,7 @@ #include <linux/llist.h> #include <linux/bitops.h> #include <linux/rbtree_augmented.h> +#include <linux/overflow.h> #include <linux/uaccess.h> #include <asm/tlbflush.h> @@ -3054,6 +3055,7 @@ finished: * @vma: vma to cover * @uaddr: target user address to start at * @kaddr: virtual address of vmalloc kernel memory + * @pgoff: offset from @kaddr to start at * @size: size of map area * * Returns: 0 for success, -Exxx on failure @@ -3066,9 +3068,15 @@ finished: * Similar to remap_pfn_range() (see mm/memory.c) */ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr, - void *kaddr, unsigned long size) + void *kaddr, unsigned long pgoff, + unsigned long size) { struct vm_struct *area; + unsigned long off; + unsigned long end_index; + + if (check_shl_overflow(pgoff, PAGE_SHIFT, &off)) + return -EINVAL; size = PAGE_ALIGN(size); @@ -3082,8 +3090,10 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr, if (!(area->flags & (VM_USERMAP | VM_DMA_COHERENT))) return -EINVAL; - if (kaddr + size > area->addr + get_vm_area_size(area)) + if (check_add_overflow(size, off, &end_index) || + end_index > get_vm_area_size(area)) return -EINVAL; + kaddr += off; do { struct page *page = vmalloc_to_page(kaddr); @@ -3122,7 +3132,7 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, unsigned long pgoff) { return remap_vmalloc_range_partial(vma, vma->vm_start, - addr + (pgoff << PAGE_SHIFT), + addr, pgoff, vma->vm_end - vma->vm_start); } EXPORT_SYMBOL(remap_vmalloc_range); |