Re: [PATCH v3 3/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas

Dan Carpenter
2023-01-14T07:58:12Z

Hi Baoquan,

url: https://github.com/intel-lab-lkp/linux/commits/Baoquan-He/mm-vmalloc-c-add-used_map-into-vmap_block-to-track-space-of-vmap_block/20230113-112149
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20230113031921.64716-4-bhe%40redhat.com
patch subject: [PATCH v3 3/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas
config: i386-randconfig-m021
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>

smatch warnings:
mm/vmalloc.c:3682 vread() error: we previously assumed 'vm' could be null (see line 3664)

vim +/vm +3682 mm/vmalloc.c

^1da177e4c3f415 Linus Torvalds 2005-04-16 3630 long vread(char *buf, char *addr, unsigned long count)
^1da177e4c3f415 Linus Torvalds 2005-04-16 3631 {
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3632 struct vmap_area *va;
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3633 struct vm_struct *vm;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3634 char *vaddr, *buf_start = buf;
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3635 unsigned long buflen = count;
129dbdf298d7383 Baoquan He 2023-01-13 3636 unsigned long n, size, flags;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3637
4aff1dc4fb3a5a3 Andrey Konovalov 2022-03-24 3638 addr = kasan_reset_tag(addr);
4aff1dc4fb3a5a3 Andrey Konovalov 2022-03-24 3639
^1da177e4c3f415 Linus Torvalds 2005-04-16 3640 /* Don't allow overflow */
^1da177e4c3f415 Linus Torvalds 2005-04-16 3641 if ((unsigned long) addr + count < count)
^1da177e4c3f415 Linus Torvalds 2005-04-16 3642 count = -(unsigned long) addr;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3643
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3644 spin_lock(&vmap_area_lock);
f181234a5a21fd0 Chen Wandun 2021-09-02 3645 va = find_vmap_area_exceed_addr((unsigned long)addr);
f608788cd2d6cae Serapheim Dimitropoulos 2021-04-29 3646 if (!va)
f608788cd2d6cae Serapheim Dimitropoulos 2021-04-29 3647 goto finished;
f181234a5a21fd0 Chen Wandun 2021-09-02 3648
f181234a5a21fd0 Chen Wandun 2021-09-02 3649 /* no intersects with alive vmap_area */
f181234a5a21fd0 Chen Wandun 2021-09-02 3650 if ((unsigned long)addr + count <= va->va_start)
f181234a5a21fd0 Chen Wandun 2021-09-02 3651 goto finished;
f181234a5a21fd0 Chen Wandun 2021-09-02 3652
f608788cd2d6cae Serapheim Dimitropoulos 2021-04-29 3653 list_for_each_entry_from(va, &vmap_area_list, list) {
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3654 if (!count)
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3655 break;
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3656
129dbdf298d7383 Baoquan He 2023-01-13 3657 vm = va->vm;
129dbdf298d7383 Baoquan He 2023-01-13 3658 flags = va->flags & VMAP_FLAGS_MASK;
129dbdf298d7383 Baoquan He 2023-01-13 3659
129dbdf298d7383 Baoquan He 2023-01-13 3660 if (!vm && !flags)
^^^
vm can be NULL if a flag in VMAP_FLAGS_MASK is set.

e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3661 continue;
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3662
129dbdf298d7383 Baoquan He 2023-01-13 3663 vaddr = (char *) va->va_start;
129dbdf298d7383 Baoquan He 2023-01-13 @3664 size = vm ? get_vm_area_size(vm) : va_size(va);
^^

129dbdf298d7383 Baoquan He 2023-01-13 3665
129dbdf298d7383 Baoquan He 2023-01-13 3666 if (addr >= vaddr + size)
^1da177e4c3f415 Linus Torvalds 2005-04-16 3667 continue;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3668 while (addr < vaddr) {
^1da177e4c3f415 Linus Torvalds 2005-04-16 3669 if (count == 0)
^1da177e4c3f415 Linus Torvalds 2005-04-16 3670 goto finished;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3671 *buf = '\0';
^1da177e4c3f415 Linus Torvalds 2005-04-16 3672 buf++;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3673 addr++;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3674 count--;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3675 }
129dbdf298d7383 Baoquan He 2023-01-13 3676 n = vaddr + size - addr;
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3677 if (n > count)
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3678 n = count;
129dbdf298d7383 Baoquan He 2023-01-13 3679
129dbdf298d7383 Baoquan He 2023-01-13 3680 if (flags & VMAP_RAM)

assume VMAP_RAM is not set

129dbdf298d7383 Baoquan He 2023-01-13 3681 vmap_ram_vread(buf, addr, n, flags);
129dbdf298d7383 Baoquan He 2023-01-13 @3682 else if (!(vm->flags & VM_IOREMAP))
^^^^^^^^^
Unchecked dereference. Should this be "flags" instead of "vm->flags"?

d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3683 aligned_vread(buf, addr, n);
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3684 else /* IOREMAP area is treated as memory hole */
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3685 memset(buf, 0, n);
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3686 buf += n;
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3687 addr += n;
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3688 count -= n;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3689 }
^1da177e4c3f415 Linus Torvalds 2005-04-16 3690 finished:
e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3691 spin_unlock(&vmap_area_lock);
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3692
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3693 if (buf == buf_start)
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3694 return 0;
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3695 /* zero-fill memory holes */
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3696 if (buf != buf_start + buflen)
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3697 memset(buf, 0, buflen - (buf - buf_start));
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3698
d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3699 return buflen;
^1da177e4c3f415 Linus Torvalds 2005-04-16 3700 }

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