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Kees Cook 72dd184323 USB: EHCI: Add register array bounds to HCS ports 
The original EHCI register struct used a trailing 0-element array for
addressing the N_PORTS-many available registers. However, after commit
a46af4ebf9 ("USB: EHCI: define extension registers like normal ones")
the 0-element array started to overlap the USBMODE extension register.

To avoid future compile-time warnings about accessing indexes within a
0-element array, rearrange the struct to actually describe the expected
layout (max 15 registers) with a union. All offsets remain the same, and
bounds checking becomes possible on accesses to port_status and hostpc.

There are no binary differences, and struct offsets continue to match.
"pahole --hex -C ehci_regs" before:

struct ehci_regs {
	u32                        command;              /*     0   0x4 */
	u32                        status;               /*   0x4   0x4 */
	u32                        intr_enable;          /*   0x8   0x4 */
	u32                        frame_index;          /*   0xc   0x4 */
	u32                        segment;              /*  0x10   0x4 */
	u32                        frame_list;           /*  0x14   0x4 */
	u32                        async_next;           /*  0x18   0x4 */
	u32                        reserved1[2];         /*  0x1c   0x8 */
	u32                        txfill_tuning;        /*  0x24   0x4 */
	u32                        reserved2[6];         /*  0x28  0x18 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	u32                        configured_flag;      /*  0x40   0x4 */
	u32                        port_status[0];       /*  0x44     0 */
	u32                        reserved3[9];         /*  0x44  0x24 */
	u32                        usbmode;              /*  0x68   0x4 */
	u32                        reserved4[6];         /*  0x6c  0x18 */
	/* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */
	u32                        hostpc[0];            /*  0x84     0 */
	u32                        reserved5[17];        /*  0x84  0x44 */
	/* --- cacheline 3 boundary (192 bytes) was 8 bytes ago --- */
	u32                        usbmode_ex;           /*  0xc8   0x4 */

	/* size: 204, cachelines: 4, members: 18 */
	/* last cacheline: 12 bytes */
};

after:

struct ehci_regs {
	u32                        command;              /*     0   0x4 */
	u32                        status;               /*   0x4   0x4 */
	u32                        intr_enable;          /*   0x8   0x4 */
	u32                        frame_index;          /*   0xc   0x4 */
	u32                        segment;              /*  0x10   0x4 */
	u32                        frame_list;           /*  0x14   0x4 */
	u32                        async_next;           /*  0x18   0x4 */
	u32                        reserved1[2];         /*  0x1c   0x8 */
	u32                        txfill_tuning;        /*  0x24   0x4 */
	u32                        reserved2[6];         /*  0x28  0x18 */
	/* --- cacheline 1 boundary (64 bytes) --- */
	u32                        configured_flag;      /*  0x40   0x4 */
	union {
		u32                port_status[15];      /*  0x44  0x3c */
		struct {
			u32        reserved3[9];         /*  0x44  0x24 */
			u32        usbmode;              /*  0x68   0x4 */
		};                                       /*  0x44  0x28 */
	};                                               /*  0x44  0x3c */
	/* --- cacheline 2 boundary (128 bytes) --- */
	u32                        reserved4;            /*  0x80   0x4 */
	u32                        hostpc[15];           /*  0x84  0x3c */
	/* --- cacheline 3 boundary (192 bytes) --- */
	u32                        reserved5[2];         /*  0xc0   0x8 */
	u32                        usbmode_ex;           /*  0xc8   0x4 */

	/* size: 204, cachelines: 4, members: 16 */
	/* last cacheline: 12 bytes */
};

With this fixed, adding -Wzero-length-bounds to the build no longer
produces several warnings like this:

In file included from drivers/usb/host/ehci-hcd.c:306:
drivers/usb/host/ehci-hub.c: In function 'ehci_port_handed_over':
drivers/usb/host/ehci-hub.c:1194:8: warning: array subscript '<unknown>' is outside the bounds of an interior zero-length array 'u32[0]' {aka 'unsigned int[]'} [-Wzero-length-bounds]
 1194 |  reg = &ehci->regs->port_status[portnum - 1];
      |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/usb/host/ehci.h:274,
                 from drivers/usb/host/ehci-hcd.c:97:
./include/linux/usb/ehci_def.h:130:7: note: while referencing 'port_status'
  130 |  u32  port_status[0]; /* up to N_PORTS */
      |       ^~~~~~~~~~~

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Al Cooper <alcooperx@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210818173018.2259231-2-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-08-18 22:28:27 +02:00
arch Merge 5.14-rc6 into usb-next 2021-08-16 09:04:28 +02:00
block block-5.14-2021-08-13 2021-08-13 13:36:42 -10:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-07-09 11:00:44 -07:00
Documentation dt-bindings: usb: mtk-musb: add MT7623 compatible 2021-08-16 18:55:47 +02:00
drivers usb: gadget: mv_u3d: request_irq() after initializing UDC 2021-08-18 16:42:09 +02:00
fs libnvdimm fixes for v5.14-rc6 2021-08-14 19:46:39 -10:00
include USB: EHCI: Add register array bounds to HCS ports 2021-08-18 22:28:27 +02:00
init Revert "mm/slub: use stackdepot to save stack trace in objects" 2021-07-17 13:27:00 -07:00
ipc Merge branch 'akpm' (patches from Andrew) 2021-07-02 12:08:10 -07:00
kernel A set of fixes for PCI/MSI and x86 interrupt startup: 2021-08-15 06:49:40 -10:00
lib lib: use PFN_PHYS() in devmem_is_allowed() 2021-08-13 14:09:32 -10:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/memcg: fix incorrect flushing of lruvec data in obj_stock 2021-08-13 14:09:32 -10:00
net Merge tag 'ieee802154-for-davem-2021-08-12' of git://git.kernel.org/pub/scm/linux/kernel/git/sschmidt/wpan 2021-08-12 11:50:17 -07:00
samples Networking fixes for 5.14-rc2, including fixes from bpf and netfilter. 2021-07-14 09:24:32 -07:00
scripts Kbuild fixes for v5.14 (2nd) 2021-08-07 10:03:02 -07:00
security bpf: Add lockdown check for probe_write_user helper 2021-08-10 10:10:10 +02:00
sound sound fixes for 5.14-rc6 2021-08-12 07:06:40 -10:00
tools libnvdimm fixes for v5.14-rc6 2021-08-14 19:46:39 -10:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-04 06:02:03 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap m68k updates for v5.14 2021-06-28 14:01:03 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Networking fixes for 5.14-rc6, including fixes from netfilter, bpf, 2021-08-12 16:24:03 -10:00
Makefile Linux 5.14-rc6 2021-08-15 13:40:53 -10:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.