[PATCH] accel/habanalabs: reject zero-element timestamp buffer allocation

[Ziyi Guo <n7l8m4@u.northwestern.edu>]

A user can issue a DRM_IOCTL_HL_MEMORY ioctl with
op=HL_MEM_OP_TS_ALLOC and num_of_elements=0. The
allocate_timestamps_buffers() function only validates the upper bound
(> TS_MAX_ELEMENTS_NUM) but not zero, allowing num_of_elements=0 to
reach vmalloc_user(0 * sizeof(u64)), which triggers WARN_ON_ONCE(!size)
in __vmalloc_node_range().

On systems with panic_on_warn=1, this allows a local user with device
access to crash the kernel.

Add a zero check to the existing validation, matching the pattern
already present in HL_MEM_OP_ALLOC (memory.c:2214).

Fixes: 9158bf69e74f ("habanalabs: Timestamps buffers registration")
Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>
---
 drivers/accel/habanalabs/common/memory.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/accel/habanalabs/common/memory.c b/drivers/accel/habanalabs/common/memory.c
index 633db4bff46f..37dbb9a013bf 100644
--- a/drivers/accel/habanalabs/common/memory.c
+++ b/drivers/accel/habanalabs/common/memory.c
@@ -2176,8 +2176,9 @@ static int allocate_timestamps_buffers(struct hl_fpriv *hpriv, struct hl_mem_in
 	struct hl_mem_mgr *mmg = &hpriv->mem_mgr;
 	struct hl_mmap_mem_buf *buf;
 
-	if (args->num_of_elements > TS_MAX_ELEMENTS_NUM) {
-		dev_err(mmg->dev, "Num of elements exceeds Max allowed number (0x%x > 0x%x)\n",
+	if (args->num_of_elements > TS_MAX_ELEMENTS_NUM ||
+				args->num_of_elements == 0) {
+		dev_err(mmg->dev, "Invalid num of elements %u, valid range [1, 0x%x]\n",
 				args->num_of_elements, TS_MAX_ELEMENTS_NUM);
 		return -EINVAL;
 	}
-- 
2.34.1