[U-Boot] [PATCH v3 1/6] fat: write: fix broken write to fragmented files

[Tom Rini]

On Tue, Nov 26, 2019 at 09:15:07AM +0100, Marek Szyprowski wrote:

> The code for handing file overwrite incorrectly assumed that the file on
> disk is always contiguous. This resulted in corrupting disk structure
> every time when write to existing fragmented file happened. Fix this
> by adding proper check for cluster discontinuity and adjust chunk size
> on each partial write.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
> Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov at toradex.com>
> Reviewed-by: Lukasz Majewski <lukma at denx.de>
> ---
>  fs/fat/fat_write.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
> index 729cf39630..6cfa5b4565 100644
> --- a/fs/fat/fat_write.c
> +++ b/fs/fat/fat_write.c
> @@ -794,6 +794,8 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
>  
>  			newclust = get_fatent(mydata, endclust);
>  
> +			if ((newclust - 1) != endclust)
> +				break;
>  			if (IS_LAST_CLUST(newclust, mydata->fatsize))
>  				break;
>  			if (CHECK_CLUST(newclust, mydata->fatsize)) {
> @@ -811,7 +813,7 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
>  			offset = 0;
>  		else
>  			offset = pos - cur_pos;
> -		wsize = min(cur_pos + actsize, filesize) - pos;
> +		wsize = min_t(unsigned long long, actsize, filesize - cur_pos);
>  		if (get_set_cluster(mydata, curclust, offset,
>  				    buffer, wsize, &actsize)) {
>  			printf("Error get-and-setting cluster\n");
> @@ -824,8 +826,6 @@ set_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos, __u8 *buffer,
>  		if (filesize <= cur_pos)
>  			break;
>  
> -		/* CHECK: newclust = get_fatent(mydata, endclust); */
> -
>  		if (IS_LAST_CLUST(newclust, mydata->fatsize))
>  			/* no more clusters */
>  			break;

Adding in Heinrich and Akashi-san for more review on this, thanks!

-- 
Tom
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