Re: [RFC PATCH v1 1/2] capability: Add cap_strings.

[Francis Laniel <flaniel@linux.microsoft.com>]

Hi.


Le lundi 27 décembre 2021, 23:26:29 CET Casey Schaufler a écrit :
> On 12/27/2021 12:54 PM, Francis Laniel wrote:
> > This array contains the capability names for the given capabilitiy.
> > For example, index CAP_BPF contains "CAP_BPF".
> > 
> > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
> > ---
> > 
> >   include/uapi/linux/capability.h |  1 +
> >   kernel/capability.c             | 45 +++++++++++++++++++++++++++++++++
> >   2 files changed, 46 insertions(+)
> > 
> > diff --git a/include/uapi/linux/capability.h
> > b/include/uapi/linux/capability.h index 463d1ba2232a..9646654d5111 100644
> > --- a/include/uapi/linux/capability.h
> > +++ b/include/uapi/linux/capability.h
> > @@ -428,5 +428,6 @@ struct vfs_ns_cap_data {
> > 
> >   #define CAP_TO_INDEX(x)     ((x) >> 5)        /* 1 << 5 == bits in __u32
> >   */
> >   #define CAP_TO_MASK(x)      (1 << ((x) & 31)) /* mask for indexed __u32
> >   */
> > 
> > +extern const char *cap_strings[];
> > 
> >   #endif /* _UAPI_LINUX_CAPABILITY_H */
> > 
> > diff --git a/kernel/capability.c b/kernel/capability.c
> > index 46a361dde042..5a2e71dcd87b 100644
> > --- a/kernel/capability.c
> > +++ b/kernel/capability.c
> > @@ -15,6 +15,7 @@
> > 
> >   #include <linux/mm.h>
> >   #include <linux/export.h>
> >   #include <linux/security.h>
> > 
> > +#include <linux/stringify.h>
> > 
> >   #include <linux/syscalls.h>
> >   #include <linux/pid_namespace.h>
> >   #include <linux/user_namespace.h>
> > 
> > @@ -27,6 +28,50 @@
> > 
> >   const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
> >   EXPORT_SYMBOL(__cap_empty_set);
> > 
> > +const char *cap_strings[] = {
> > +	[CAP_CHOWN] = __stringify_1(CAP_CHOWN),
> 
> I may just be old and slow, but why is this better than
> 
> 	[CAP_CHOWN] = "CAP_CHOWN",

Good catch, thank you for it, I just replaced the __stringify_1() by quotes.
I thought of using __stringify_() because at first I thought of adding a new 
macro which would both define a new capability as well as adding to this array.

But I think it is better to with this simple way rather than doing complicated 
stuff.

> > +	[CAP_DAC_OVERRIDE] = __stringify_1(CAP_DAC_OVERRIDE),
> > +	[CAP_DAC_READ_SEARCH] = __stringify_1(CAP_DAC_READ_SEARCH),
> > +	[CAP_FOWNER] = __stringify_1(CAP_FOWNER),
> > +	[CAP_FSETID] = __stringify_1(CAP_FSETID),
> > +	[CAP_KILL] = __stringify_1(CAP_KILL),
> > +	[CAP_SETGID] = __stringify_1(CAP_SETGID),
> > +	[CAP_SETUID] = __stringify_1(CAP_SETUID),
> > +	[CAP_SETPCAP] = __stringify_1(CAP_SETPCAP),
> > +	[CAP_LINUX_IMMUTABLE] = __stringify_1(CAP_LINUX_IMMUTABLE),
> > +	[CAP_NET_BIND_SERVICE] = __stringify_1(CAP_NET_BIND_SERVICE),
> > +	[CAP_NET_BROADCAST] = __stringify_1(CAP_NET_BROADCAST),
> > +	[CAP_NET_ADMIN] = __stringify_1(CAP_NET_ADMIN),
> > +	[CAP_NET_RAW] = __stringify_1(CAP_NET_RAW),
> > +	[CAP_IPC_LOCK] = __stringify_1(CAP_IPC_LOCK),
> > +	[CAP_IPC_OWNER] = __stringify_1(CAP_IPC_OWNER),
> > +	[CAP_SYS_MODULE] = __stringify_1(CAP_SYS_MODULE),
> > +	[CAP_SYS_RAWIO] = __stringify_1(CAP_SYS_RAWIO),
> > +	[CAP_SYS_CHROOT] = __stringify_1(CAP_SYS_CHROOT),
> > +	[CAP_SYS_PTRACE] = __stringify_1(CAP_SYS_PTRACE),
> > +	[CAP_SYS_PACCT] = __stringify_1(CAP_SYS_PACCT),
> > +	[CAP_SYS_ADMIN] = __stringify_1(CAP_SYS_ADMIN),
> > +	[CAP_SYS_BOOT] = __stringify_1(CAP_SYS_BOOT),
> > +	[CAP_SYS_NICE] = __stringify_1(CAP_SYS_NICE),
> > +	[CAP_SYS_RESOURCE] = __stringify_1(CAP_SYS_RESOURCE),
> > +	[CAP_SYS_TIME] = __stringify_1(CAP_SYS_TIME),
> > +	[CAP_SYS_TTY_CONFIG] = __stringify_1(CAP_SYS_TTY_CONFIG),
> > +	[CAP_MKNOD] = __stringify_1(CAP_MKNOD),
> > +	[CAP_LEASE] = __stringify_1(CAP_LEASE),
> > +	[CAP_AUDIT_WRITE] = __stringify_1(CAP_AUDIT_WRITE),
> > +	[CAP_AUDIT_CONTROL] = __stringify_1(CAP_AUDIT_CONTROL),
> > +	[CAP_SETFCAP] = __stringify_1(CAP_SETFCAP),
> > +	[CAP_MAC_OVERRIDE] = __stringify_1(CAP_MAC_OVERRIDE),
> > +	[CAP_MAC_ADMIN] = __stringify_1(CAP_MAC_ADMIN),
> > +	[CAP_SYSLOG] = __stringify_1(CAP_SYSLOG),
> > +	[CAP_WAKE_ALARM] = __stringify_1(CAP_WAKE_ALARM),
> > +	[CAP_BLOCK_SUSPEND] = __stringify_1(CAP_BLOCK_SUSPEND),
> > +	[CAP_AUDIT_READ] = __stringify_1(CAP_AUDIT_READ),
> > +	[CAP_PERFMON] = __stringify_1(CAP_PERFMON),
> > +	[CAP_BPF] = __stringify_1(CAP_BPF),
> > +	[CAP_CHECKPOINT_RESTORE] = __stringify_1(CAP_CHECKPOINT_RESTORE),
> > +};
> > +
> > 
> >   int file_caps_enabled = 1;
> >   
> >   static int __init file_caps_disable(char *str)