This is a note to let you know that I've just added the patch titled
HID: bpf: actually free hdev memory after attaching a HID-BPF program
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hid-bpf-actually-free-hdev-memory-after-attaching-a-hid-bpf-program.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 89be8aa5b0ecb3b729c7bcff64bb2af7921fec63 Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <bentiss@xxxxxxxxxx>
Date: Wed, 24 Jan 2024 12:26:58 +0100
Subject: HID: bpf: actually free hdev memory after attaching a HID-BPF program
From: Benjamin Tissoires <bentiss@xxxxxxxxxx>
commit 89be8aa5b0ecb3b729c7bcff64bb2af7921fec63 upstream.
Turns out that I got my reference counts wrong and each successful
bus_find_device() actually calls get_device(), and we need to manually
call put_device().
Ensure each bus_find_device() gets a matching put_device() when releasing
the bpf programs and fix all the error paths.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: f5c27da4e3c8 ("HID: initial BPF implementation")
Link: https://lore.kernel.org/r/20240124-b4-hid-bpf-fixes-v2-2-052520b1e5e6@xxxxxxxxxx
Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/hid/bpf/hid_bpf_dispatch.c | 29 +++++++++++++++++++++++------
drivers/hid/bpf/hid_bpf_jmp_table.c | 20 +++++++++++++++++---
2 files changed, 40 insertions(+), 9 deletions(-)
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -292,7 +292,7 @@ hid_bpf_attach_prog(unsigned int hid_id,
struct hid_device *hdev;
struct bpf_prog *prog;
struct device *dev;
- int fd;
+ int err, fd;
if (!hid_bpf_ops)
return -EINVAL;
@@ -311,14 +311,24 @@ hid_bpf_attach_prog(unsigned int hid_id,
* on errors or when it'll be detached
*/
prog = bpf_prog_get(prog_fd);
- if (IS_ERR(prog))
- return PTR_ERR(prog);
+ if (IS_ERR(prog)) {
+ err = PTR_ERR(prog);
+ goto out_dev_put;
+ }
fd = do_hid_bpf_attach_prog(hdev, prog_fd, prog, flags);
- if (fd < 0)
- bpf_prog_put(prog);
+ if (fd < 0) {
+ err = fd;
+ goto out_prog_put;
+ }
return fd;
+
+ out_prog_put:
+ bpf_prog_put(prog);
+ out_dev_put:
+ put_device(dev);
+ return err;
}
/**
@@ -345,8 +355,10 @@ hid_bpf_allocate_context(unsigned int hi
hdev = to_hid_device(dev);
ctx_kern = kzalloc(sizeof(*ctx_kern), GFP_KERNEL);
- if (!ctx_kern)
+ if (!ctx_kern) {
+ put_device(dev);
return NULL;
+ }
ctx_kern->ctx.hid = hdev;
@@ -363,10 +375,15 @@ noinline void
hid_bpf_release_context(struct hid_bpf_ctx *ctx)
{
struct hid_bpf_ctx_kern *ctx_kern;
+ struct hid_device *hid;
ctx_kern = container_of(ctx, struct hid_bpf_ctx_kern, ctx);
+ hid = (struct hid_device *)ctx_kern->ctx.hid; /* ignore const */
kfree(ctx_kern);
+
+ /* get_device() is called by bus_find_device() */
+ put_device(&hid->dev);
}
/**
--- a/drivers/hid/bpf/hid_bpf_jmp_table.c
+++ b/drivers/hid/bpf/hid_bpf_jmp_table.c
@@ -196,6 +196,7 @@ static void __hid_bpf_do_release_prog(in
static void hid_bpf_release_progs(struct work_struct *work)
{
int i, j, n, map_fd = -1;
+ bool hdev_destroyed;
if (!jmp_table.map)
return;
@@ -220,6 +221,12 @@ static void hid_bpf_release_progs(struct
if (entry->hdev) {
hdev = entry->hdev;
type = entry->type;
+ /*
+ * hdev is still valid, even if we are called after hid_destroy_device():
+ * when hid_bpf_attach() gets called, it takes a ref on the dev through
+ * bus_find_device()
+ */
+ hdev_destroyed = hdev->bpf.destroyed;
hid_bpf_populate_hdev(hdev, type);
@@ -232,12 +239,19 @@ static void hid_bpf_release_progs(struct
if (test_bit(next->idx, jmp_table.enabled))
continue;
- if (next->hdev == hdev && next->type == type)
+ if (next->hdev == hdev && next->type == type) {
+ /*
+ * clear the hdev reference and decrement the device ref
+ * that was taken during bus_find_device() while calling
+ * hid_bpf_attach()
+ */
next->hdev = NULL;
+ put_device(&hdev->dev);
+ }
}
- /* if type was rdesc fixup, reconnect device */
- if (type == HID_BPF_PROG_TYPE_RDESC_FIXUP)
+ /* if type was rdesc fixup and the device is not gone, reconnect device */
+ if (type == HID_BPF_PROG_TYPE_RDESC_FIXUP && !hdev_destroyed)
hid_bpf_reconnect(hdev);
}
}
Patches currently in stable-queue which might be from bentiss@xxxxxxxxxx are
queue-6.6/hid-bpf-actually-free-hdev-memory-after-attaching-a-hid-bpf-program.patch
queue-6.6/hid-bpf-remove-double-fdget.patch
