linux-kernel - Re: [PATCH v2] vfs: fix put_compat_statfs64() does not handle errors

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Date:   Tue, 29 Nov 2016 13:55:52 +0800
From:   Li Wang <wangli.ahau@...il.com>
To:     Li Wang <liwang@...hat.com>
Cc:     adilger@...ger.ca, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vfs: fix put_compat_statfs64() does not handle errors

sorry, ping for comments~



On 15 November 2016 at 17:19, Li Wang <liwang@...hat.com> wrote:
> put_compat_statfs64() does NOT return -1 and setting errno to EOVERFLOW
> when some variables(like: f_bsize) overflowed in the returned struct.
>
> The reason is that the ubuf->f_blocks is __u64 type, it couldn't be
> 4bits as the judgement in put_comat_statfs64(). Here correct the
> __u32 variables(in struct compat_statfs64) for comparison.
>
> reproducer:
> step1. mount hugetlbfs with two different pagesize on ppc64 arch.
>
> $ hugeadm --pool-pages-max 16M:0
> $ hugeadm --create-mount
> $ mount | grep -i hugetlbfs
> none on /var/lib/hugetlbfs/pagesize-16MB type hugetlbfs (rw,relatime,seclabel,pagesize=16777216)
> none on /var/lib/hugetlbfs/pagesize-16GB type hugetlbfs (rw,relatime,seclabel,pagesize=17179869184)
>
> step2. compile & run this C program.
>
> $ cat statfs64_test.c
>
>  #define _LARGEFILE64_SOURCE
>  #include <stdio.h>
>  #include <sys/syscall.h>
>  #include <sys/statfs.h>
>
>  int main()
>  {
>         struct statfs64 sb;
>         int err;
>
>         err = syscall(SYS_statfs64, "/var/lib/hugetlbfs/pagesize-16GB", sizeof(sb), &sb);
>         if (err)
>                 return -1;
>
>         printf("sizeof f_bsize = %d, f_bsize=%ld\n", sizeof(sb.f_bsize), sb.f_bsize);
>
>         return 0;
>  }
>
> $ gcc -m32 statfs64_test.c
> $ ./a.out
> sizeof f_bsize = 4, f_bsize=0
>
> Signed-off-by: Li Wang <liwang@...hat.com>
> ---
>  fs/compat.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/compat.c b/fs/compat.c
> index bd064a2..543b48c 100644
> --- a/fs/compat.c
> +++ b/fs/compat.c
> @@ -253,9 +253,9 @@ static int put_compat_statfs(struct compat_statfs __user *ubuf, struct kstatfs *
>
>  static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstatfs *kbuf)
>  {
> -       if (sizeof ubuf->f_blocks == 4) {
> -               if ((kbuf->f_blocks | kbuf->f_bfree | kbuf->f_bavail |
> -                    kbuf->f_bsize | kbuf->f_frsize) & 0xffffffff00000000ULL)
> +       if (sizeof(ubuf->f_bsize) == 4) {
> +               if ((kbuf->f_type | kbuf->f_bsize | kbuf->f_namelen |
> +                    kbuf->f_frsize | kbuf->f_flags) & 0xffffffff00000000ULL)
>                         return -EOVERFLOW;
>                 /* f_files and f_ffree may be -1; it's okay
>                  * to stuff that into 32 bits */
> --
> 1.8.3.1
>



-- 
Regards,
Li Wang
Email: wangli.ahau@...il.com