Re: + mm-fs-prepare-for-non-page-entries-in-page-cache-radix-trees.patch added to -mm tree

[Johannes Weiner]

On Tue, Feb 04, 2014 at 03:14:49PM -0800, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> @@ -307,14 +331,15 @@ void truncate_inode_pages_range(struct a
>  	index = start;
>  	for ( ; ; ) {
>  		cond_resched();
> -		if (!pagevec_lookup(&pvec, mapping, index,
> -			min(end - index, (pgoff_t)PAGEVEC_SIZE))) {
> +		if (!__pagevec_lookup(&pvec, mapping, index,
> +			min(end - index, (pgoff_t)PAGEVEC_SIZE),
> +			indices)) {
>  			if (index == start)
>  				break;
>  			index = start;
>  			continue;
>  		}
> -		if (index == start && pvec.pages[0]->index >= end) {
> +		if (index == start && indices[0] >= end) {
>  			pagevec_release(&pvec);
>  			break;
>  		}

There is a missing pagevec_remove_exceptionals(), which can crash the
kernel when pagevec_release() passes the non-page pointers to the page
allocator.

Andrew, could you please include this incremental fix?

---
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: [patch] mm + fs: prepare for non-page entries in page cache radix
 trees fix

__pagevec_lookup() stores exceptional entries in the pagevec.  They
must be pruned before passing the pagevec along to pagevec_release()
or the kernel crashes when these non-page pointers reach the page
allocator.

Add a missing pagevec_remove_exceptionals() in the truncate path.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
 mm/truncate.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/truncate.c b/mm/truncate.c
index b0f4d4bee8ab..5fafca2ed3d2 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -340,6 +340,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
 			continue;
 		}
 		if (index == start && indices[0] >= end) {
+			pagevec_remove_exceptionals(&pvec);
 			pagevec_release(&pvec);
 			break;
 		}
-- 
1.9.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/