On 8/3/21 11:34 AM, Pavel Begunkov wrote:

On 8/3/21 8:47 AM, Sudip Mukherjee wrote:

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On Mon, Aug 2, 2021 at 12:55 PM Pavel Begunkov [off-list ref] wrote:

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On 8/1/21 9:28 PM, Sudip Mukherjee wrote:

quoted

On Sun, Aug 1, 2021 at 9:52 AM Pavel Begunkov [off-list ref] wrote:

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On 8/1/21 1:10 AM, Pavel Begunkov wrote:

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On 7/31/21 7:21 PM, Sudip Mukherjee wrote:

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Hi Jens, Pavel,

We had been running syzkaller on v5.10.y and a "KASAN:
stack-out-of-bounds in iov_iter_revert" was being reported on it. I
got some time to check that today and have managed to get a syzkaller
reproducer. I dont have a C reproducer which I can share but I can use
the syz-reproducer to reproduce this with v5.14-rc3 and also with
next-20210730.

Can you try out the diff below? Not a full-fledged fix, but need to
check a hunch.

If that's important, I was using this branch:
git://git.kernel.dk/linux-block io_uring-5.14

Or better this one, just in case it ooopses on warnings.

I tested this one on top of "git://git.kernel.dk/linux-block
io_uring-5.14" and the issue was still seen, but after the BUG trace I
got lots of "truncated wr" message. The trace is:

That's interesting, thanks
Can you share the syz reproducer?

Unfortunately I dont have a C reproducer, but this is the reproducer
for syzkaller:

Thanks. Maybe I'm not perfectly familiar with syz, but were there
any options? Like threaded, collide, etc.?

Never mind, reproduced the issue.

fwiw, I was too optimistic with u16 in the diff, but if
replaced with size_t, it solves the out-of-bounds bug,
but it has another issue.

In any case, need to patch it up, thanks

-- 
Pavel Begunkov