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Subject[PATCH 3/7] aio: sanitize ki_list handling
Date
Instead of handcoded non-null checks always initialize ki_list to an
empty list and use list_empty / list_empty_careful on it. While we're
at it also error out on a double call to kiocb_set_cancel_fn instead
of ignoring it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/aio.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 7c1855afd723..18507743757a 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -553,13 +553,12 @@ void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
struct kioctx *ctx = req->ki_ctx;
unsigned long flags;

- spin_lock_irqsave(&ctx->ctx_lock, flags);
-
- if (!req->ki_list.next)
- list_add(&req->ki_list, &ctx->active_reqs);
+ if (WARN_ON_ONCE(!list_empty(&req->ki_list)))
+ return;

+ spin_lock_irqsave(&ctx->ctx_lock, flags);
+ list_add_tail(&req->ki_list, &ctx->active_reqs);
req->ki_cancel = cancel;
-
spin_unlock_irqrestore(&ctx->ctx_lock, flags);
}
EXPORT_SYMBOL(kiocb_set_cancel_fn);
@@ -1039,7 +1038,7 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
goto out_put;

percpu_ref_get(&ctx->reqs);
-
+ INIT_LIST_HEAD(&req->ki_list);
req->ki_ctx = ctx;
return req;
out_put:
@@ -1107,7 +1106,7 @@ static void aio_complete(struct kiocb *kiocb, long res, long res2)
file_end_write(file);
}

- if (iocb->ki_list.next) {
+ if (!list_empty_careful(&iocb->ki_list)) {
unsigned long flags;

spin_lock_irqsave(&ctx->ctx_lock, flags);
--
2.17.0
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