diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2021-10-02 15:02:17 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-10-05 12:52:03 +0200 |
| commit | 846cbf98cbef20376b1a95fa3734c435543f3519 (patch) | |
| tree | 1bd9a61c7a2a2d57121f906b7e763272175a826f | |
| parent | ef53d3db1c59fe7893baf4dca851d3d3daff04b6 (diff) | |
| download | linux-846cbf98cbef20376b1a95fa3734c435543f3519.tar.bz2 | |
USB: EHCI: Improve port index sanitizing
Now that Kees Cook has added a definition for HCS_N_PORTS_MAX in
commit 72dd1843232c ("USB: EHCI: Add register array bounds to HCS
ports"), the code in ehci_hub_control() which sanitizes port index
values can be improved a little.
The idea behind this change is that it prevents a possible
out-of-bounds pointer computation, which the compiler might be able to
detect since the port_status[] array now has a fixed length rather
than a variable length.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20211002190217.GA537967@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/host/ehci-hub.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c index c4f6a2559a98..efe30e3be22f 100644 --- a/drivers/usb/host/ehci-hub.c +++ b/drivers/usb/host/ehci-hub.c @@ -745,12 +745,13 @@ int ehci_hub_control( unsigned selector; /* - * Avoid underflow while calculating (wIndex & 0xff) - 1. - * The compiler might deduce that wIndex can never be 0 and then - * optimize away the tests for !wIndex below. + * Avoid out-of-bounds values while calculating the port index + * from wIndex. The compiler doesn't like pointers to invalid + * addresses, even if they are never used. */ - temp = wIndex & 0xff; - temp -= (temp > 0); + temp = (wIndex - 1) & 0xff; + if (temp >= HCS_N_PORTS_MAX) + temp = 0; status_reg = &ehci->regs->port_status[temp]; hostpc_reg = &ehci->regs->hostpc[temp]; |