From: Kanchan Joshi <joshi.k@samsung.com>
To: Christoph Hellwig <hch@lst.de>
Cc: kbusch@kernel.org, sagi@grimberg.me, linux-nvme@lists.infradead.org
Subject: Re: [PATCH] nvme: don't allow unprivileged Write Zeroes passthrough on read-only FDs
Date: Thu, 1 Dec 2022 04:50:12 +0530 [thread overview]
Message-ID: <20221130232012.GA24451@test-zns> (raw)
In-Reply-To: <20221129090016.1311006-1-hch@lst.de>
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On Tue, Nov 29, 2022 at 10:00:16AM +0100, Christoph Hellwig wrote:
>Unfortunately Write Zeroes is coded as a no data transfer opcode in NVMe,
>so don't allow it on a read-only FD for unprivileged users.
>
>Fixes: 855b7717f44b ("nvme: fine-granular CAP_SYS_ADMIN for nvme io commands")
>Signed-off-by: Christoph Hellwig <hch@lst.de>
>---
> drivers/nvme/host/ioctl.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
>index 9550a69029b368..8aefe9c904dc9a 100644
>--- a/drivers/nvme/host/ioctl.c
>+++ b/drivers/nvme/host/ioctl.c
>@@ -45,7 +45,7 @@ static bool nvme_cmd_allowed(struct nvme_ns *ns, struct nvme_command *c,
> * special file is open for writing, but always allow I/O commands that
> * transfer data from the controller.
> */
>- if (nvme_is_write(c))
>+ if (nvme_is_write(c) || c->common.opcode == nvme_cmd_write_zeroes)
> return mode & FMODE_WRITE;
I was thinking why check for write_zeroes should not go inside nvme_is_write
itself. Then I saw various callers of nvme_is_write, and that killed the
thought.
Another thought is - does it make sense to include nvme_cmd_flush too?
That is also declared as no-data-transfer in spec. Flush alone can't
make any difference when writes are not allowed in first place. So this
is about whether we care for empty flushes.
And on spec - not sure whether the criteria has changed of late. copy
command also does not involve data-transfer but bit is set there.
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next prev parent reply other threads:[~2022-11-30 23:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20221129090709epcas5p21176e0faa7914cea52aab2e8fa95c2db@epcas5p2.samsung.com>
2022-11-29 9:00 ` [PATCH] nvme: don't allow unprivileged Write Zeroes passthrough on read-only FDs Christoph Hellwig
2022-11-29 17:54 ` Chaitanya Kulkarni
2022-11-30 8:34 ` Sagi Grimberg
2022-11-30 23:20 ` Kanchan Joshi [this message]
2022-12-01 16:07 ` Keith Busch
2022-12-01 16:09 ` Christoph Hellwig
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