| Message ID | 20210818043035.1308062-2-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | USB: EHCI: Add register array bounds to HCS ports | expand |
On Wed, Aug 18, 2021 at 7:30 AM Kees Cook <keescook@chromium.org> wrote: > > The original EHCI register struct used a trailing 0-element array for > addressing the N_PORTS-many available registers. However, after > commit a46af4ebf9ff ("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. ... > /* HOSTPC: offset 0x84 */ > - u32 hostpc[0]; /* HOSTPC extension */ > + u32 hostpc[HCS_N_PORTS_MAX]; > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ > #define HOSTPC_PSPD (3<<25) /* Port speed detection */ > > - u32 reserved5[17]; > + u32 reserved5[2]; Shouldn't it be rather [17 - PORT_MAX]? for accuracy? Or also a union approach?
On Tue, Aug 17, 2021 at 09:30:33PM -0700, Kees Cook wrote: > The original EHCI register struct used a trailing 0-element array for > addressing the N_PORTS-many available registers. However, after > commit a46af4ebf9ff ("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. Two comments... > --- > include/linux/usb/ehci_def.h | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/include/linux/usb/ehci_def.h b/include/linux/usb/ehci_def.h > index 78e006355557..5398f571113b 100644 > --- a/include/linux/usb/ehci_def.h > +++ b/include/linux/usb/ehci_def.h > @@ -45,6 +45,7 @@ struct ehci_caps { > #define HCS_PORTROUTED(p) ((p)&(1 << 7)) /* true: port routing */ > #define HCS_PPC(p) ((p)&(1 << 4)) /* true: port power control */ > #define HCS_N_PORTS(p) (((p)>>0)&0xf) /* bits 3:0, ports on HC */ > +#define HCS_N_PORTS_MAX 0xf /* N_PORTS valid 0x1-0xF */ I would prefer to see this value in decimal. It seems very odd to say something like "The maximum number of ports is 0xf". > > u32 hcc_params; /* HCCPARAMS - offset 0x8 */ > /* EHCI 1.1 addendum */ > @@ -126,8 +127,9 @@ struct ehci_regs { > u32 configured_flag; > #define FLAG_CF (1<<0) /* true: we'll support "high speed" */ > > - /* PORTSC: offset 0x44 */ > - u32 port_status[0]; /* up to N_PORTS */ > + union { > + /* PORTSC: offset 0x44 */ > + u32 port_status[HCS_N_PORTS_MAX]; Please don't lose the second comment. > /* EHCI 1.1 addendum */ > #define PORTSC_SUSPEND_STS_ACK 0 > #define PORTSC_SUSPEND_STS_NYET 1 > @@ -164,28 +166,28 @@ struct ehci_regs { > #define PORT_CSC (1<<1) /* connect status change */ > #define PORT_CONNECT (1<<0) /* device connected */ > #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC) > - > - u32 reserved3[9]; > - > - /* USBMODE: offset 0x68 */ > - u32 usbmode; /* USB Device mode */ > + struct { > + u32 reserved3[9]; > + /* USBMODE: offset 0x68 */ > + u32 usbmode; /* USB Device mode */ > + }; > #define USBMODE_SDIS (1<<3) /* Stream disable */ > #define USBMODE_BE (1<<2) /* BE/LE endianness select */ > #define USBMODE_CM_HC (3<<0) /* host controller mode */ > #define USBMODE_CM_IDLE (0<<0) /* idle state */ > - > - u32 reserved4[6]; > + }; > + u32 reserved4; > > /* Moorestown has some non-standard registers, partially due to the fact that > * its EHCI controller has both TT and LPM support. HOSTPCx are extensions to > * PORTSCx > */ > /* HOSTPC: offset 0x84 */ > - u32 hostpc[0]; /* HOSTPC extension */ > + u32 hostpc[HCS_N_PORTS_MAX]; > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ > #define HOSTPC_PSPD (3<<25) /* Port speed detection */ > > - u32 reserved5[17]; > + u32 reserved5[2]; > > /* USBMODE_EX: offset 0xc8 */ > u32 usbmode_ex; /* USB Device mode extension */ Otherwise okay. Alan Stern
On Wed, Aug 18, 2021 at 12:48:17PM +0300, Andy Shevchenko wrote: > On Wed, Aug 18, 2021 at 7:30 AM Kees Cook <keescook@chromium.org> wrote: > > > > The original EHCI register struct used a trailing 0-element array for > > addressing the N_PORTS-many available registers. However, after > > commit a46af4ebf9ff ("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. > > ... > > > /* HOSTPC: offset 0x84 */ > > - u32 hostpc[0]; /* HOSTPC extension */ > > + u32 hostpc[HCS_N_PORTS_MAX]; > > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ > > #define HOSTPC_PSPD (3<<25) /* Port speed detection */ > > > > - u32 reserved5[17]; > > + u32 reserved5[2]; > > Shouldn't it be rather [17 - PORT_MAX]? for accuracy? > Or also a union approach? It's okay to use [2] here. The only purpose is to ensure that the following usbmode_ex field is allocated at offset 0xc8; there's no special intrinsic meaning to that 17 value. Alan Stern
On Wed, Aug 18, 2021 at 10:44:42AM -0400, Alan Stern wrote: > On Tue, Aug 17, 2021 at 09:30:33PM -0700, Kees Cook wrote: > > The original EHCI register struct used a trailing 0-element array for > > addressing the N_PORTS-many available registers. However, after > > commit a46af4ebf9ff ("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. > > Two comments... > > > --- > > include/linux/usb/ehci_def.h | 24 +++++++++++++----------- > > 1 file changed, 13 insertions(+), 11 deletions(-) > > > > diff --git a/include/linux/usb/ehci_def.h b/include/linux/usb/ehci_def.h > > index 78e006355557..5398f571113b 100644 > > --- a/include/linux/usb/ehci_def.h > > +++ b/include/linux/usb/ehci_def.h > > @@ -45,6 +45,7 @@ struct ehci_caps { > > #define HCS_PORTROUTED(p) ((p)&(1 << 7)) /* true: port routing */ > > #define HCS_PPC(p) ((p)&(1 << 4)) /* true: port power control */ > > #define HCS_N_PORTS(p) (((p)>>0)&0xf) /* bits 3:0, ports on HC */ > > +#define HCS_N_PORTS_MAX 0xf /* N_PORTS valid 0x1-0xF */ > > I would prefer to see this value in decimal. It seems very odd to say > something like "The maximum number of ports is 0xf". Okay, done. > > > > > u32 hcc_params; /* HCCPARAMS - offset 0x8 */ > > /* EHCI 1.1 addendum */ > > @@ -126,8 +127,9 @@ struct ehci_regs { > > u32 configured_flag; > > #define FLAG_CF (1<<0) /* true: we'll support "high speed" */ > > > > - /* PORTSC: offset 0x44 */ > > - u32 port_status[0]; /* up to N_PORTS */ > > + union { > > + /* PORTSC: offset 0x44 */ > > + u32 port_status[HCS_N_PORTS_MAX]; > > Please don't lose the second comment. I've put it back. It seemed redundant in the face of HCS_N_PORTS_MAX being there now. > > > /* EHCI 1.1 addendum */ > > #define PORTSC_SUSPEND_STS_ACK 0 > > #define PORTSC_SUSPEND_STS_NYET 1 > > @@ -164,28 +166,28 @@ struct ehci_regs { > > #define PORT_CSC (1<<1) /* connect status change */ > > #define PORT_CONNECT (1<<0) /* device connected */ > > #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC) > > - > > - u32 reserved3[9]; > > - > > - /* USBMODE: offset 0x68 */ > > - u32 usbmode; /* USB Device mode */ > > + struct { > > + u32 reserved3[9]; > > + /* USBMODE: offset 0x68 */ > > + u32 usbmode; /* USB Device mode */ > > + }; > > #define USBMODE_SDIS (1<<3) /* Stream disable */ > > #define USBMODE_BE (1<<2) /* BE/LE endianness select */ > > #define USBMODE_CM_HC (3<<0) /* host controller mode */ > > #define USBMODE_CM_IDLE (0<<0) /* idle state */ > > - > > - u32 reserved4[6]; > > + }; > > + u32 reserved4; > > > > /* Moorestown has some non-standard registers, partially due to the fact that > > * its EHCI controller has both TT and LPM support. HOSTPCx are extensions to > > * PORTSCx > > */ > > /* HOSTPC: offset 0x84 */ > > - u32 hostpc[0]; /* HOSTPC extension */ > > + u32 hostpc[HCS_N_PORTS_MAX]; > > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ > > #define HOSTPC_PSPD (3<<25) /* Port speed detection */ > > > > - u32 reserved5[17]; > > + u32 reserved5[2]; > > > > /* USBMODE_EX: offset 0xc8 */ > > u32 usbmode_ex; /* USB Device mode extension */ > > Otherwise okay. Thanks!
diff --git a/include/linux/usb/ehci_def.h b/include/linux/usb/ehci_def.h index 78e006355557..5398f571113b 100644 --- a/include/linux/usb/ehci_def.h +++ b/include/linux/usb/ehci_def.h @@ -45,6 +45,7 @@ struct ehci_caps { #define HCS_PORTROUTED(p) ((p)&(1 << 7)) /* true: port routing */ #define HCS_PPC(p) ((p)&(1 << 4)) /* true: port power control */ #define HCS_N_PORTS(p) (((p)>>0)&0xf) /* bits 3:0, ports on HC */ +#define HCS_N_PORTS_MAX 0xf /* N_PORTS valid 0x1-0xF */ u32 hcc_params; /* HCCPARAMS - offset 0x8 */ /* EHCI 1.1 addendum */ @@ -126,8 +127,9 @@ struct ehci_regs { u32 configured_flag; #define FLAG_CF (1<<0) /* true: we'll support "high speed" */ - /* PORTSC: offset 0x44 */ - u32 port_status[0]; /* up to N_PORTS */ + union { + /* PORTSC: offset 0x44 */ + u32 port_status[HCS_N_PORTS_MAX]; /* EHCI 1.1 addendum */ #define PORTSC_SUSPEND_STS_ACK 0 #define PORTSC_SUSPEND_STS_NYET 1 @@ -164,28 +166,28 @@ struct ehci_regs { #define PORT_CSC (1<<1) /* connect status change */ #define PORT_CONNECT (1<<0) /* device connected */ #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC) - - u32 reserved3[9]; - - /* USBMODE: offset 0x68 */ - u32 usbmode; /* USB Device mode */ + struct { + u32 reserved3[9]; + /* USBMODE: offset 0x68 */ + u32 usbmode; /* USB Device mode */ + }; #define USBMODE_SDIS (1<<3) /* Stream disable */ #define USBMODE_BE (1<<2) /* BE/LE endianness select */ #define USBMODE_CM_HC (3<<0) /* host controller mode */ #define USBMODE_CM_IDLE (0<<0) /* idle state */ - - u32 reserved4[6]; + }; + u32 reserved4; /* Moorestown has some non-standard registers, partially due to the fact that * its EHCI controller has both TT and LPM support. HOSTPCx are extensions to * PORTSCx */ /* HOSTPC: offset 0x84 */ - u32 hostpc[0]; /* HOSTPC extension */ + u32 hostpc[HCS_N_PORTS_MAX]; #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ #define HOSTPC_PSPD (3<<25) /* Port speed detection */ - u32 reserved5[17]; + u32 reserved5[2]; /* USBMODE_EX: offset 0xc8 */ u32 usbmode_ex; /* USB Device mode extension */
The original EHCI register struct used a trailing 0-element array for addressing the N_PORTS-many available registers. However, after commit a46af4ebf9ff ("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 Fixes: a46af4ebf9ff ("USB: EHCI: define extension registers like normal ones") Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/usb/ehci_def.h | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-)