From: Alan Stern <stern@rowland.harvard.edu> To: Kees Cook <keescook@chromium.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Al Cooper <alcooperx@gmail.com>, linux-usb@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Arnd Bergmann <arnd@arndb.de>, Florian Fainelli <f.fainelli@gmail.com>, Andy Shevchenko <andy.shevchenko@gmail.com>, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 2/2] USB: EHCI: Add alias for Broadcom INSNREG Date: Wed, 18 Aug 2021 10:57:36 -0400 [thread overview] Message-ID: <20210818145736.GD193695@rowland.harvard.edu> (raw) In-Reply-To: <20210818043035.1308062-3-keescook@chromium.org> On Tue, Aug 17, 2021 at 09:30:34PM -0700, Kees Cook wrote: > Refactor struct ehci_regs to avoid accessing beyond the end of > port_status. This change results in no difference in the resulting > object code. > > Avoids several warnings when building with -Warray-bounds: > > drivers/usb/host/ehci-brcm.c: In function 'ehci_brcm_reset': > drivers/usb/host/ehci-brcm.c:113:32: warning: array subscript 16 is above array bounds of 'u32[15]' {aka 'unsigned int[15]'} [-Warray-bounds] > 113 | ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > In file included from drivers/usb/host/ehci.h:274, > from drivers/usb/host/ehci-brcm.c:15: > ./include/linux/usb/ehci_def.h:132:7: note: while referencing 'port_status' > 132 | u32 port_status[HCS_N_PORTS_MAX]; > | ^~~~~~~~~~~ > > Note that the documentation around this proprietary register is > confusing. If "USB_EHCI_INSNREG00" is at port_status[0x0f], its offset > would be 0x80 (not 0x90). The code uses port_status[0x10], so is that > not using "USB_EHCI_INSNREG00"? I suspect the 0x90 value in the comment is a typo for 0x80. > Perhaps port_status[0x10] is USB_EHCI_INSNREG01 and port_status[0x12] > is USB_EHCI_INSNREG03? If so, the union could be adjusted to better > represent the layout. > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Al Cooper <alcooperx@gmail.com> > Cc: Alan Stern <stern@rowland.harvard.edu> > Cc: linux-usb@vger.kernel.org > Cc: bcm-kernel-feedback-list@broadcom.com > Suggested-by: Arnd Bergmann <arnd@arndb.de> > Fixes: 9df231511bd6 ("usb: ehci: Add new EHCI driver for Broadcom STB SoC's") > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > drivers/usb/host/ehci-brcm.c | 11 +++++------ > include/linux/usb/ehci_def.h | 16 ++++++++++++++-- > 2 files changed, 19 insertions(+), 8 deletions(-) > > diff --git a/drivers/usb/host/ehci-brcm.c b/drivers/usb/host/ehci-brcm.c > index 3e0ebe8cc649..5d232d3701f9 100644 > --- a/drivers/usb/host/ehci-brcm.c > +++ b/drivers/usb/host/ehci-brcm.c > @@ -110,8 +110,8 @@ static int ehci_brcm_reset(struct usb_hcd *hcd) > * bus usage > * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 @ 0x90 This last comment line is no longer necessary, thanks to the revised port definitions. And since it is actively misleading, with the 0x90 instead of 0x80, I think it should be removed entirely. > */ > - ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]); > - ehci_writel(ehci, 0x00000001, &ehci->regs->port_status[0x12]); > + ehci_writel(ehci, 0x00800040, &ehci->regs->brcm_insnreg[0]); > + ehci_writel(ehci, 0x00000001, &ehci->regs->brcm_insnreg[2]); > > return ehci_setup(hcd); > } > @@ -223,11 +223,10 @@ static int __maybe_unused ehci_brcm_resume(struct device *dev) > /* > * SWLINUX-1705: Avoid OUT packet underflows during high memory > * bus usage > - * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 > - * @ 0x90 > + * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 @ 0x90 Same here. > */ > - ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]); > - ehci_writel(ehci, 0x00000001, &ehci->regs->port_status[0x12]); > + ehci_writel(ehci, 0x00800040, &ehci->regs->brcm_insnreg[0]); > + ehci_writel(ehci, 0x00000001, &ehci->regs->brcm_insnreg[2]); > > ehci_resume(hcd, false); > > diff --git a/include/linux/usb/ehci_def.h b/include/linux/usb/ehci_def.h > index 5398f571113b..86f0909cab99 100644 > --- a/include/linux/usb/ehci_def.h > +++ b/include/linux/usb/ehci_def.h > @@ -182,11 +182,23 @@ struct ehci_regs { > * its EHCI controller has both TT and LPM support. HOSTPCx are extensions to > * PORTSCx > */ > - /* HOSTPC: offset 0x84 */ > - u32 hostpc[HCS_N_PORTS_MAX]; > + union { > + /* HOSTPC: offset 0x84 */ > + u32 hostpc[HCS_N_PORTS_MAX]; > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ > #define HOSTPC_PSPD (3<<25) /* Port speed detection */ > > + /* > + * This was originally documented as: > + * "port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 @ 0x90" > + * but this doesn't make sense: the code was using > + * port_status[0x10]. port_status[0x0f] would be reserved4. > + * Also, none of these are near 0x90. port_status[0x10] is > + * offset 0x84, and port_status[0x0f] would be 0x80. > + */ This comment is entirely inappropriate. It's the sort of thing that belongs in the git history, not in the code. > + u32 brcm_insnreg[3]; Given the notation in the original comments, perhaps it would be better to define this as: struct { /* Broadcom proprietary registers */ u32 brcm_insnreg01; /* offset 0x84 */ u32 brcm_insnreg02; u32 brcm_insnreg03; }; I don't know. It would be nice to hear from somebody at Broadcom. Alan Stern > + }; > + > u32 reserved5[2]; > > /* USBMODE_EX: offset 0xc8 */ > -- > 2.30.2 >
next prev parent reply other threads:[~2021-08-18 14:57 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-18 4:30 [PATCH 0/2] USB: EHCI: Add register array bounds to HCS ports Kees Cook 2021-08-18 4:30 ` [PATCH 1/2] " Kees Cook 2021-08-18 9:48 ` Andy Shevchenko 2021-08-18 15:02 ` Alan Stern 2021-08-18 14:44 ` Alan Stern 2021-08-18 17:17 ` Kees Cook 2021-08-18 4:30 ` [PATCH 2/2] USB: EHCI: Add alias for Broadcom INSNREG Kees Cook 2021-08-18 14:57 ` Alan Stern [this message] 2021-08-18 17:15 ` Kees Cook
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