Re: [PATCH 27/32] aio: sanitize ki_list handling
From: Jeff Moyer <hidden>
Date: 2018-01-10 21:29:30
Also in:
linux-fsdevel, lkml, netdev
Christoph Hellwig [off-list ref] writes:
Instead of handcoded non-null checks always initialize ki_list to an empty list and use list_empty / list_empty_careful on it.
Yeah, who knows why list_empty wasn't used from the beginning. In the past, tricks were played by overwriting list pointers with non-null, but that wasn't the case here.
quoted hunk
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> --- fs/aio.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)diff --git a/fs/aio.c b/fs/aio.c index 496b50f9e9b1..fe241b5b44b2 100644 --- a/fs/aio.c +++ b/fs/aio.c@@ -555,13 +555,12 @@ 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;
So, this changes behavior from quietly overwriting the prior cancel function to not doing it. I don't think it matters one bit, though. Callers shouldn't do that. Acked-by: Jeff Moyer <redacted> -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: <a href=mailto:"aart@kvack.org">aart@kvack.org</a>