[PATCH v4] acpi: nfit: vmalloc-out-of-bounds Read in acpi_nfit_ctl

[Suraj Sonawane <surajsonawane0215@gmail.com>]

Fix an issue detected by syzbot with KASAN:

BUG: KASAN: vmalloc-out-of-bounds in cmd_to_func drivers/acpi/nfit/
core.c:416 [inline]
BUG: KASAN: vmalloc-out-of-bounds in acpi_nfit_ctl+0x20e8/0x24a0
drivers/acpi/nfit/core.c:459

The issue occurs in cmd_to_func when the call_pkg->nd_reserved2
array is accessed without verifying that call_pkg points to a buffer
that is appropriately sized as a struct nd_cmd_pkg. This can lead
to out-of-bounds access and undefined behavior if the buffer does not
have sufficient space.

To address this, a check was added in acpi_nfit_ctl() to ensure that
buf is not NULL and that buf_len is less than sizeof(*call_pkg)
before accessing it. This ensures safe access to the members of
call_pkg, including the nd_reserved2 array.

Reported-by: syzbot+7534f060ebda6b8b51b3@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7534f060ebda6b8b51b3
Tested-by: syzbot+7534f060ebda6b8b51b3@syzkaller.appspotmail.com
Fixes: ebe9f6f19d80 ("acpi/nfit: Fix bus command validation")
Signed-off-by: Suraj Sonawane <surajsonawane0215@gmail.com>
---
V1: https://lore.kernel.org/lkml/20241111080429.9861-1-surajsonawane0215@gmail.com/ 
V2: Initialized `out_obj` to `NULL` in `acpi_nfit_ctl()` to prevent
potential uninitialized variable usage if condition is true.
V3: Changed the condition to if (!buf || buf_len < sizeof(*call_pkg))
and updated the Fixes tag to reference the correct commit.
V4: Removed the explicit cast to maintain the original code style.

 drivers/acpi/nfit/core.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 5429ec9ef..84d8eef2a 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -454,8 +454,15 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	if (cmd_rc)
 		*cmd_rc = -EINVAL;
 
-	if (cmd == ND_CMD_CALL)
+	if (cmd == ND_CMD_CALL) {
+		if (!buf || buf_len < sizeof(*call_pkg)) {
+			rc = -EINVAL;
+			goto out;
+		}
+
 		call_pkg = buf;
+	}
+
 	func = cmd_to_func(nfit_mem, cmd, call_pkg, &family);
 	if (func < 0)
 		return func;
-- 
2.34.1