From: Alan Stern stern@rowland.harvard.edu

[ Upstream commit a6b87bfc2ab5bccb7ad953693c85d9062aef3fdd ]

Testing by the syzbot fuzzer showed that the HID core gets a shift-out-of-bounds exception when it tries to convert a 32-bit quantity to a 0-bit quantity. Ideally this should never occur, but there are buggy devices and some might have a report field with size set to zero; we shouldn't reject the report or the device just because of that.

Instead, harden the s32ton() routine so that it returns a reasonable result instead of crashing when it is called with the number of bits set to 0 -- the same as what snto32() does.

Signed-off-by: Alan Stern stern@rowland.harvard.edu Reported-by: syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-usb/68753a08.050a0220.33d347.0008.GAE@google.c... Tested-by: syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com Fixes: dde5845a529f ("[PATCH] Generic HID layer - code split") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/613a66cd-4309-4bce-a4f7-2905f9bce0c9@rowland.harvar... Signed-off-by: Benjamin Tissoires bentiss@kernel.org [ s32ton() was moved by c653ffc28340 ("HID: stop exporting hid_snto32()"). Minor context change fixed. ] Signed-off-by: Wenshan Lan jetlan9@163.com --- drivers/hid/hid-core.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index ed65523d77c2..c8cca0c7ec67 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1354,7 +1354,12 @@ EXPORT_SYMBOL_GPL(hid_snto32);

static u32 s32ton(__s32 value, unsigned n) { - s32 a = value >> (n - 1); + s32 a; + if (!value || !n) + return 0; + + a = value >> (n - 1); + if (a && a != -1) return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1; return value & ((1 << n) - 1);