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

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Date:   Tue, 29 Nov 2016 15:09:58 -0700
From:   Andreas Dilger <adilger@...ger.ca>
To:     Li Wang <liwang@...hat.com>
Cc:     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


> On Nov 15, 2016, at 2:19 AM, 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>

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> ---
> 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
> 


Cheers, Andreas






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