[PATCH v5 3/3] aio_free_ring: don't do page_count(NULL)

From: Oleg Nesterov
Date: Fri Jun 19 2015 - 14:20:31 EST


aio_free_ring() can actually see the NULL page in ->ring_pages[],
this can happen if aio_setup_ring() fails.

And in this case page_count(ctx->ring_pages[i]) can OOPS.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
---
fs/aio.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 4a360be..9bc1335 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -292,12 +292,12 @@ static void aio_free_ring(struct kioctx *ctx)
put_aio_ring_file(ctx);

for (i = 0; i < ctx->nr_pages; i++) {
- struct page *page;
- pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
- page_count(ctx->ring_pages[i]));
- page = ctx->ring_pages[i];
+ struct page *page = ctx->ring_pages[i];
if (!page)
continue;
+
+ pr_debug("pid(%d) [%d] page->count=%d\n",
+ current->pid, i, page_count(page));
ctx->ring_pages[i] = NULL;
put_page(page);
}
--
1.5.5.1

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