From d776369a9eded071df83e4738e1572c4c5b912d7 Mon Sep 17 00:00:00 2001 From: Karl Mehltretter Date: Thu, 27 Aug 2026 07:37:41 +0200 Subject: [PATCH] ACPI: pfr_update: zero-initialize capability query result query_capability() copies four ACPI buffers into fixed-size fields using the firmware-supplied lengths. The existing overflow guard rejects oversized buffers, but shorter buffers are accepted and leave trailing bytes of the stack-allocated cap_hdr uninitialized. PFRU_IOC_QUERY_CAP then copies the entire structure to userspace. Zero-initialize cap_hdr before querying the firmware. This preserves the existing handling of short firmware responses while preventing disclosure of kernel stack data. Oversized buffers remain rejected. A QEMU _DSM returning one-byte buffers reproduced nonzero stack suffix bytes in all four fields. With this change, the ioctl still succeeds and each unwritten suffix is zero-filled, while 64-byte buffers continue to return -EINVAL. Fixes: 0db89fa243e5 ("ACPI: Introduce Platform Firmware Runtime Update device driver") Reported-by: Sashiko Closes: https://sashiko.dev/#/patchset/1a001e1fee9.637da6dc3533246.238498880682901704%40a0rg.com Cc: All applicable Signed-off-by: Karl Mehltretter Link: https://patch.msgid.link/20260827053741.79425-1-kmehltretter@gmail.com Signed-off-by: Rafael J. Wysocki --- drivers/acpi/pfr_update.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/pfr_update.c b/drivers/acpi/pfr_update.c index 9afd2c52fdbd..98ace679601b 100644 --- a/drivers/acpi/pfr_update.c +++ b/drivers/acpi/pfr_update.c @@ -422,7 +422,7 @@ static int start_update(int action, struct pfru_device *pfru_dev) static long pfru_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { - struct pfru_update_cap_info cap_hdr; + struct pfru_update_cap_info cap_hdr = {}; struct pfru_device *pfru_dev = to_pfru_dev(file); void __user *p = (void __user *)arg; u32 rev;