From 9f2892f7233a8f1320fe671d0f95f122191bfbcd Mon Sep 17 00:00:00 2001 From: Benjamin Tissoires Date: Thu, 10 Jul 2025 16:01:33 +0200 Subject: [PATCH] HID: core: ensure the allocated report buffer can contain the reserved report ID commit 4f15ee98304b96e164ff2340e1dfd6181c3f42aa upstream. When the report ID is not used, the low level transport drivers expect the first byte to be 0. However, currently the allocated buffer not account for that extra byte, meaning that instead of having 8 guaranteed bytes for implement to be working, we only have 7. Reported-by: Alan Stern Closes: https://lore.kernel.org/linux-input/c75433e0-9b47-4072-bbe8-b1d14ea97b13@rowland.harvard.edu/ Cc: stable@vger.kernel.org Suggested-by: Alan Stern Link: https://patch.msgid.link/20250710-report-size-null-v2-1-ccf922b7c4e5@kernel.org Signed-off-by: Benjamin Tissoires Signed-off-by: Greg Kroah-Hartman --- drivers/hid/hid-core.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 126acf5441c8c..37ec5dba3ba3b 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1662,9 +1662,12 @@ u8 *hid_alloc_report_buf(struct hid_report *report, gfp_t flags) /* * 7 extra bytes are necessary to achieve proper functionality * of implement() working on 8 byte chunks + * 1 extra byte for the report ID if it is null (not used) so + * we can reserve that extra byte in the first position of the buffer + * when sending it to .raw_request() */ - u32 len = hid_report_len(report) + 7; + u32 len = hid_report_len(report) + 7 + (report->id == 0); return kzalloc(len, flags); } -- 2.47.3