Re: [PATCH 08/15] binfmt_flat: add endianess annotations

[Vladimir Murzin]

On 6/10/19 10:20 PM, Christoph Hellwig wrote:
> Most binfmt_flat on-disk fields are big endian.  Use the proper __be32
> type where applicable.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>  fs/binfmt_flat.c | 26 ++++++++++++++++----------
>  1 file changed, 16 insertions(+), 10 deletions(-)

Tested-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
Reviewed-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>

> 
> diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
> index 6ae0f9af3fc9..6c1848dee724 100644
> --- a/fs/binfmt_flat.c
> +++ b/fs/binfmt_flat.c
> @@ -421,7 +421,8 @@ static int load_flat_file(struct linux_binprm *bprm,
>  	unsigned long textpos, datapos, realdatastart;
>  	u32 text_len, data_len, bss_len, stack_len, full_data, flags;
>  	unsigned long len, memp, memp_size, extra, rlim;
> -	u32 __user *reloc, *rp;
> +	__be32 __user *reloc;
> +	u32 __user *rp;
>  	struct inode *inode;
>  	int i, rev, relocs;
>  	loff_t fpos;
> @@ -594,7 +595,7 @@ static int load_flat_file(struct linux_binprm *bprm,
>  			goto err;
>  		}
>  
> -		reloc = (u32 __user *)
> +		reloc = (__be32 __user *)
>  			(datapos + (ntohl(hdr->reloc_start) - text_len));
>  		memp = realdatastart;
>  		memp_size = len;
> @@ -619,7 +620,7 @@ static int load_flat_file(struct linux_binprm *bprm,
>  				MAX_SHARED_LIBS * sizeof(u32),
>  				FLAT_DATA_ALIGN);
>  
> -		reloc = (u32 __user *)
> +		reloc = (__be32 __user *)
>  			(datapos + (ntohl(hdr->reloc_start) - text_len));
>  		memp = textpos;
>  		memp_size = len;
> @@ -785,15 +786,16 @@ static int load_flat_file(struct linux_binprm *bprm,
>  		u32 __maybe_unused persistent = 0;
>  		for (i = 0; i < relocs; i++) {
>  			u32 addr, relval;
> +			__be32 tmp;
>  
>  			/*
>  			 * Get the address of the pointer to be
>  			 * relocated (of course, the address has to be
>  			 * relocated first).
>  			 */
> -			if (get_user(relval, reloc + i))
> +			if (get_user(tmp, reloc + i))
>  				return -EFAULT;
> -			relval = ntohl(relval);
> +			relval = ntohl(tmp);
>  			addr = flat_get_relocate_addr(relval);
>  			rp = (u32 __user *)calc_reloc(addr, libinfo, id, 1);
>  			if (rp == (u32 __user *)RELOC_FAILED) {
> @@ -812,8 +814,13 @@ static int load_flat_file(struct linux_binprm *bprm,
>  				 * Do the relocation.  PIC relocs in the data section are
>  				 * already in target order
>  				 */
> -				if ((flags & FLAT_FLAG_GOTPIC) == 0)
> -					addr = ntohl(addr);
> +				if ((flags & FLAT_FLAG_GOTPIC) == 0) {
> +					/*
> +					 * Meh, the same value can have a different
> +					 * byte order based on a flag..
> +					 */
> +					addr = ntohl((__force __be32)addr);
> +				}
>  				addr = calc_reloc(addr, libinfo, id, 0);
>  				if (addr == RELOC_FAILED) {
>  					ret = -ENOEXEC;
> @@ -828,11 +835,10 @@ static int load_flat_file(struct linux_binprm *bprm,
>  		}
>  	} else {
>  		for (i = 0; i < relocs; i++) {
> -			u32 relval;
> +			__be32 relval;
>  			if (get_user(relval, reloc + i))
>  				return -EFAULT;
> -			relval = ntohl(relval);
> -			old_reloc(relval);
> +			old_reloc(ntohl(relval));
>  		}
>  	}
>  
>