5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alan Stern stern@rowland.harvard.edu
commit 64f2657b579343cf923aa933f08074e6258eb07b upstream.
A report in 2019 by the syzbot fuzzer was found to be connected to two errors in the HID core associated with Resolution Multipliers. One of the errors was fixed by commit ea427a222d8b ("HID: core: Fix deadloop in hid_apply_multiplier."), but the other has not been fixed.
This error arises because hid_apply_multipler() assumes that every Resolution Multiplier control is contained in a Logical Collection, i.e., there's no way the routine can ever set multiplier_collection to NULL. This is in spite of the fact that the function starts with a big comment saying:
* "The Resolution Multiplier control must be contained in the same * Logical Collection as the control(s) to which it is to be applied. ... * If no Logical Collection is * defined, the Resolution Multiplier is associated with all * controls in the report." * HID Usage Table, v1.12, Section 4.3.1, p30 * * Thus, search from the current collection upwards until we find a * logical collection...
The comment and the code overlook the possibility that none of the collections found may be a Logical Collection.
The fix is to set the multiplier_collection pointer to NULL if the collection found isn't a Logical Collection.
Reported-by: syzbot+ec5f884c4a135aa0dbb9@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000109c040597dc5843@google.com/ Signed-off-by: Alan Stern stern@rowland.harvard.edu Cc: Peter Hutterer peter.hutterer@who-t.net Fixes: 5a4abb36f312 ("HID: core: process the Resolution Multiplier") Cc: stable@vger.kernel.org Signed-off-by: Jiri Kosina jkosina@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/hid/hid-core.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1117,6 +1117,8 @@ static void hid_apply_multiplier(struct while (multiplier_collection->parent_idx != -1 && multiplier_collection->type != HID_COLLECTION_LOGICAL) multiplier_collection = &hid->collection[multiplier_collection->parent_idx]; + if (multiplier_collection->type != HID_COLLECTION_LOGICAL) + multiplier_collection = NULL;
effective_multiplier = hid_calculate_multiplier(hid, multiplier);