linux-kernel - [PATCHv3] habanalabs: fix potential spectre v1 gadgets

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Date:   Wed,  2 Feb 2022 20:11:00 +0100
From:   Jordy Zomer <jordy@...ing.systems>
To:     linux-kernel@...r.kernel.org
Cc:     Jordy Zomer <jordy@...ing.systems>,
        Oded Gabbay <ogabbay@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ofir Bitton <obitton@...ana.ai>,
        Dani Liberman <dliberman@...ana.ai>,
        Yuri Nudelman <ynudelman@...ana.ai>,
        Sagiv Ozeri <sozeri@...ana.ai>, Koby Elbaz <kelbaz@...ana.ai>,
        farah kassabri <fkassabri@...ana.ai>
Subject: [PATCHv3] habanalabs: fix potential spectre v1 gadgets

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@...ing.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