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Subject: Re: [PATCHv3] habanalabs: fix potential spectre v1 gadgets
From:   Jordy Zomer <jordy@pwning.systems>
In-Reply-To: <20220202191104.3526448-1-jordy@pwning.systems>
Date:   Wed, 2 Feb 2022 20:13:46 +0100
Cc:     Oded Gabbay <ogabbay@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ofir Bitton <obitton@habana.ai>,
        Dani Liberman <dliberman@habana.ai>,
        Yuri Nudelman <ynudelman@habana.ai>,
        Sagiv Ozeri <sozeri@habana.ai>, Koby Elbaz <kelbaz@habana.ai>,
        farah kassabri <fkassabri@habana.ai>
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Message-Id: <EC712491-2563-4822-A54B-244638EB656E@pwning.systems>
References: <YfrVOylHQYqjiWJ5@kroah.com>
 <20220202191104.3526448-1-jordy@pwning.systems>
To:     linux-kernel@vger.kernel.org
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Sorry! Removed the message and hope the line-wrapping is correct now :)

> On 2 Feb 2022, at 20:11, Jordy Zomer <jordy@pwning.systems> wrote:
> 
> It appears like nr could be a Spectre v1 gadget as it's supplied by a
> user and used as an array index. Prevent the contents of kernel memory
> being leaked  to userspace via speculative execution by using
> array_index_nospec.
> 
> Signed-off-by: Jordy Zomer <jordy@pwning.systems>
> 
> ---
> Changes v1 -> v2: Added the correct offsets
> Changes v2 -> v3: Fixed line-wrapping
> ---
> drivers/misc/habanalabs/common/habanalabs_ioctl.c | 3 +++
> 1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/misc/habanalabs/common/habanalabs_ioctl.c b/drivers/misc/habanalabs/common/habanalabs_ioctl.c
> index 3ba3a8ffda3e..c1cdf712a10d 100644
> --- a/drivers/misc/habanalabs/common/habanalabs_ioctl.c
> +++ b/drivers/misc/habanalabs/common/habanalabs_ioctl.c
> @@ -14,6 +14,7 @@
> #include <linux/fs.h>
> #include <linux/uaccess.h>
> #include <linux/slab.h>
> +#include <linux/nospec.h>
> 
> static u32 hl_debug_struct_size[HL_DEBUG_OP_TIMESTAMP + 1] = {
> 	[HL_DEBUG_OP_ETR] = sizeof(struct hl_debug_params_etr),
> @@ -849,6 +850,7 @@ long hl_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
> 	}
> 
> 	if ((nr >= HL_COMMAND_START) && (nr < HL_COMMAND_END)) {
> +		nr = array_index_nospec(nr, HL_COMMAND_END);
> 		ioctl = &hl_ioctls[nr];
> 	} else {
> 		dev_err(hdev->dev, "invalid ioctl: pid=%d, nr=0x%02x\n",
> @@ -872,6 +874,7 @@ long hl_ioctl_control(struct file *filep, unsigned int cmd, unsigned long arg)
> 	}
> 
> 	if (nr == _IOC_NR(HL_IOCTL_INFO)) {
> +		nr = array_index_nospec(nr, _IOC_NR(HL_IOCTL_INFO)+1);
> 		ioctl = &hl_ioctls_control[nr];
> 	} else {
> 		dev_err(hdev->dev_ctrl, "invalid ioctl: pid=%d, nr=0x%02x\n",
> -- 
> 2.27.0
>