[PATCH] ubifs: Handle LPT corruption better in ubifs_garbage_collect_leb()

[PATCH] ubifs: Handle LPT corruption better in ubifs_garbage_collect_leb()

[Richard Weinberger]

If ubifs_garbage_collect_leb() notes a LPT problem, empty LEB, but
LPT has it makred as used, an ubifs_assert() is not enough.
We have to abort GC. Otherwise list_entry() returns an invalid
scan object and the kernel crashes.

c: <stable@vger.kernel.org>
Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
Signed-off-by: Richard Weinberger <richard@nod.at>
---
 fs/ubifs/gc.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c
index a03a47cf880d..11c09ce3c795 100644
--- a/fs/ubifs/gc.c
+++ b/fs/ubifs/gc.c
@@ -513,7 +513,13 @@ int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 	if (IS_ERR(sleb))
 		return PTR_ERR(sleb);
 
-	ubifs_assert(!list_empty(&sleb->nodes));
+	if (list_empty(&sleb->nodes)) {
+		ubifs_err(c, "Bad accouting information, LEB %i is marked as used but no nodes found!",
+			  lnum);
+		dump_stack();
+		return -EUCLEAN;
+	}
+
 	snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
 
 	if (snod->type == UBIFS_IDX_NODE) {
-- 
2.18.0

Re: [PATCH] ubifs: Handle LPT corruption better in ubifs_garbage_collect_leb()

[Sascha Hauer]

Hi Richard,

On Wed, Jul 04, 2018 at 04:02:30PM +0200, Richard Weinberger wrote:
> If ubifs_garbage_collect_leb() notes a LPT problem, empty LEB, but
> LPT has it makred as used, an ubifs_assert() is not enough.
> We have to abort GC. Otherwise list_entry() returns an invalid
> scan object and the kernel crashes.
> 
> c: <stable@vger.kernel.org>
> Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
>  fs/ubifs/gc.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)

What happened to this patch? It never made it anywhere. I just stumbled
over this issue and found this patch afterwards.

> 
> diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c
> index a03a47cf880d..11c09ce3c795 100644
> --- a/fs/ubifs/gc.c
> +++ b/fs/ubifs/gc.c
> @@ -513,7 +513,13 @@ int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
>  	if (IS_ERR(sleb))
>  		return PTR_ERR(sleb);
>  
> -	ubifs_assert(!list_empty(&sleb->nodes));
> +	if (list_empty(&sleb->nodes)) {
> +		ubifs_err(c, "Bad accouting information, LEB %i is marked as used but no nodes found!",
> +			  lnum);
> +		dump_stack();
> +		return -EUCLEAN;
> +	}

This changes the behaviour. With ubifs_assert() UBIFS goes readonly, but
with this change it stays rw. Is this intended?

Sascha

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Re: [PATCH] ubifs: Handle LPT corruption better in ubifs_garbage_collect_leb()

[Richard Weinberger]

Sascha,

----- Ursprüngliche Mail -----
> What happened to this patch? It never made it anywhere. I just stumbled
> over this issue and found this patch afterwards.

I have withdrawn this patch because it cures only a symptom and not
the root cause. The root cause is a LPT corruption.
IIRC I saw the problem while investigating into another problem which
caused UBIFS corruptions.

Thanks,
//richard