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authorJohannes Berg <johannes.berg@intel.com>2022-03-16 23:27:51 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-04-08 15:23:00 +0300
commitcdcaec46a6b22a7c2a44366115d424b38a5cee55 (patch)
treecc16acd7f79ff9cad9cc4da1da85246467b71ad2 /include
parent677a5f6c81b5eae856757f5b625a20f130963793 (diff)
downloadlinux-cdcaec46a6b22a7c2a44366115d424b38a5cee55.tar.xz
rfkill: make new event layout opt-in
commit 54f586a9153201c6cff55e1f561990c78bd99aa7 upstream. Again new complaints surfaced that we had broken the ABI here, although previously all the userspace tools had agreed that it was their mistake and fixed it. Yet now there are cases (e.g. RHEL) that want to run old userspace with newer kernels, and thus are broken. Since this is a bit of a whack-a-mole thing, change the whole extensibility scheme of rfkill to no longer just rely on the message lengths, but instead require userspace to opt in via a new ioctl to a given maximum event size that it is willing to understand. By default, set that to RFKILL_EVENT_SIZE_V1 (8), so that the behaviour for userspace not calling the ioctl will look as if it's just running on an older kernel. Fixes: 14486c82612a ("rfkill: add a reason to the HW rfkill state") Cc: stable@vger.kernel.org # 5.11+ Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Kalle Valo <kvalo@kernel.org> Link: https://lore.kernel.org/r/20220316212749.16491491b270.Ifcb1950998330a596f29a2a162e00b7546a1d6d0@changeid Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/uapi/linux/rfkill.h14
1 files changed, 12 insertions, 2 deletions
diff --git a/include/uapi/linux/rfkill.h b/include/uapi/linux/rfkill.h
index 9b77cfc42efa..283c5a7b3f2c 100644
--- a/include/uapi/linux/rfkill.h
+++ b/include/uapi/linux/rfkill.h
@@ -159,8 +159,16 @@ struct rfkill_event_ext {
* old behaviour for all userspace, unless it explicitly opts in to the
* rules outlined here by using the new &struct rfkill_event_ext.
*
- * Userspace using &struct rfkill_event_ext must adhere to the following
- * rules
+ * Additionally, some other userspace (bluez, g-s-d) was reading with a
+ * large size but as streaming reads rather than message-based, or with
+ * too strict checks for the returned size. So eventually, we completely
+ * reverted this, and extended messages need to be opted in to by using
+ * an ioctl:
+ *
+ * ioctl(fd, RFKILL_IOCTL_MAX_SIZE, sizeof(struct rfkill_event_ext));
+ *
+ * Userspace using &struct rfkill_event_ext and the ioctl must adhere to
+ * the following rules:
*
* 1. accept short writes, optionally using them to detect that it's
* running on an older kernel;
@@ -175,6 +183,8 @@ struct rfkill_event_ext {
#define RFKILL_IOC_MAGIC 'R'
#define RFKILL_IOC_NOINPUT 1
#define RFKILL_IOCTL_NOINPUT _IO(RFKILL_IOC_MAGIC, RFKILL_IOC_NOINPUT)
+#define RFKILL_IOC_MAX_SIZE 2
+#define RFKILL_IOCTL_MAX_SIZE _IOW(RFKILL_IOC_MAGIC, RFKILL_IOC_EXT_SIZE, __u32)
/* and that's all userspace gets */