[PATCH] lseek: tighten error checking and allow negative offsets for SEEK_END

[PATCH] lseek: tighten error checking and allow negative offsets for SEEK_END

[Uwe Kleine-König]

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 fs/fs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/fs.c b/fs/fs.c
index e7b696591433..1901c94ad1ea 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -910,6 +910,8 @@ loff_t lseek(int fildes, loff_t offset, int whence)
 	case SEEK_SET:
 		if (f->size != FILE_SIZE_STREAM && offset > f->size)
 			goto out;
+		if (offset < 0)
+			goto out;
 		pos = offset;
 		break;
 	case SEEK_CUR:
@@ -918,9 +920,9 @@ loff_t lseek(int fildes, loff_t offset, int whence)
 		pos = f->pos + offset;
 		break;
 	case SEEK_END:
-		if (offset)
+		if (offset > 0)
 			goto out;
-		pos = f->size;
+		pos = f->size + offset;
 		break;
 	default:
 		goto out;
-- 
2.11.0


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Re: [PATCH] lseek: tighten error checking and allow negative offsets for SEEK_END

[Sascha Hauer]

On Thu, Mar 02, 2017 at 03:37:03PM +0100, Uwe Kleine-König wrote:
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>  fs/fs.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Applied, thanks

Sascha

> 
> diff --git a/fs/fs.c b/fs/fs.c
> index e7b696591433..1901c94ad1ea 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -910,6 +910,8 @@ loff_t lseek(int fildes, loff_t offset, int whence)
>  	case SEEK_SET:
>  		if (f->size != FILE_SIZE_STREAM && offset > f->size)
>  			goto out;
> +		if (offset < 0)
> +			goto out;
>  		pos = offset;
>  		break;
>  	case SEEK_CUR:
> @@ -918,9 +920,9 @@ loff_t lseek(int fildes, loff_t offset, int whence)
>  		pos = f->pos + offset;
>  		break;
>  	case SEEK_END:
> -		if (offset)
> +		if (offset > 0)
>  			goto out;
> -		pos = f->size;
> +		pos = f->size + offset;
>  		break;
>  	default:
>  		goto out;
> -- 
> 2.11.0
> 
> 
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