diff options
authorJann Horn <jannh@google.com>2020-04-20 18:14:11 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-04-29 16:31:27 +0200
commitd8da38eafa38b03c741aa63f688e5a77343a77be (patch)
parente6755e71c77520ae6e08c99d213448914245b515 (diff)
vmalloc: fix remap_vmalloc_range() bounds checks
commit bdebd6a2831b6fab69eb85cee74a8ba77f1a1cc2 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
4 files changed, 18 insertions, 7 deletions
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 5c5f161763c8..c4147e50af98 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -250,7 +250,8 @@ static int vmcoredd_mmap_dumps(struct vm_area_struct *vma, unsigned long dst,
if (start < offset + dump->size) {
tsz = min(offset + (u64)dump->size - start, (u64)size);
buf = dump->buf + start - offset;
- if (remap_vmalloc_range_partial(vma, dst, buf, tsz)) {
+ if (remap_vmalloc_range_partial(vma, dst, buf, 0,
+ tsz)) {
ret = -EFAULT;
goto out_unlock;
@@ -607,7 +608,7 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)start, size);
kaddr = elfnotes_buf + start - elfcorebuf_sz - vmcoredd_orig_sz;
if (remap_vmalloc_range_partial(vma, vma->vm_start + len,
- kaddr, tsz))
+ kaddr, 0, tsz))
goto fail;
size -= tsz;
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 6ae8dd1d784f..206957b1b54d 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -103,7 +103,7 @@ extern void vunmap(const void *addr);
extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
unsigned long uaddr, void *kaddr,
- unsigned long size);
+ unsigned long pgoff, unsigned long size);
extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
unsigned long pgoff);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index be65161f9753..11d0f0b6ec79 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -31,6 +31,7 @@
#include <linux/compiler.h>
#include <linux/llist.h>
#include <linux/bitops.h>
+#include <linux/overflow.h>
#include <linux/uaccess.h>
#include <asm/tlbflush.h>
@@ -2228,6 +2229,7 @@ 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
@@ -2240,9 +2242,15 @@ 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);
@@ -2256,8 +2264,10 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
if (!(area->flags & VM_USERMAP))
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);
@@ -2296,7 +2306,7 @@ 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);
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 96e7969c473a..d774717cd906 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -418,7 +418,7 @@ static int mdpy_mmap(struct mdev_device *mdev, struct vm_area_struct *vma)
return -EINVAL;
return remap_vmalloc_range_partial(vma, vma->vm_start,
- mdev_state->memblk,
+ mdev_state->memblk, 0,
vma->vm_end - vma->vm_start);