linux-kernel - Re: [PATCH] UBIFS: fix assertion in layout_in

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Date:	Sun, 14 Aug 2016 11:00:33 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Vincent Stehlé <vincent.stehle@...el.com>
Cc:	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Subject: Re: [PATCH] UBIFS: fix assertion in layout_in_gaps()

Vincent,

On Fri, Aug 12, 2016 at 3:26 PM, Vincent Stehlé
<vincent.stehle@...el.com> wrote:
> An assertion in layout_in_gaps() verifies that the gap_lebs pointer is
> below the maximum bound. When computing this maximum bound the idx_lebs
> count is multiplied by sizeof(int), while C pointers arithmetic does take
> into account the size of the pointed elements implicitly already. Remove
> the multiplication to fix the assertion.
>
> Fixes: 1e51764a3c2ac05a ("UBIFS: add new flash file system")
> Signed-off-by: Vincent Stehlé <vincent.stehle@...el.com>
> Cc: Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
> ---
>  fs/ubifs/tnc_commit.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
> index b45345d..51157da 100644
> --- a/fs/ubifs/tnc_commit.c
> +++ b/fs/ubifs/tnc_commit.c
> @@ -370,7 +370,7 @@ static int layout_in_gaps(struct ubifs_info *c, int cnt)
>
>         p = c->gap_lebs;
>         do {
> -               ubifs_assert(p < c->gap_lebs + sizeof(int) * c->lst.idx_lebs);
> +               ubifs_assert(p < c->gap_lebs + c->lst.idx_lebs);

Good catch! Did you hit this assertion or was it found by review?
I bet the latter since it is here since ever and given the wrongness
it is unlikely to trigger.

-- 
Thanks,
//richard