Hi James, would you mind taking the following into
security-testing?
The securebits are used by passing them to prctl with the
PR_{S,G}ET_SECUREBITS commands. But the defines must be
shifted to be used in prctl, which begs to be confused and
misused by userspace. So define some more convenient
values for userspace to specify. This way userspace does
prctl(PR_SET_SECUREBITS, SECBIT_NOROOT);
instead of
prctl(PR_SET_SECUREBITS, 1 << SECURE_NOROOT);
(Thanks to Michael for the idea)
This patch also adds include/linux/securebits to the installed headers.
Then perhaps it can be included by glibc's sys/prctl.h.
Changelog:
Oct 29: Stephen Rothwell points out that issecure can
be under __KERNEL__.
Oct 14: (Suggestions by Michael Kerrisk):
1. spell out SETUID in SECBIT_NO_SETUID*
2. SECBIT_X_LOCKED does not imply SECBIT_X
3. add definitions for keepcaps
Oct 14: As suggested by Michael Kerrisk, don't
use SB_* as that convention is already in
use. Use SECBIT_ prefix instead.
Signed-off-by: Serge E. Hallyn <[email protected]>
Acked-by: Andrew G. Morgan <[email protected]>
Acked-by: Michael Kerrisk <[email protected]>
Cc: Ulrich Drepper <[email protected]>
Cc: James Morris <[email protected]>
---
include/linux/Kbuild | 1 +
include/linux/securebits.h | 24 ++++++++++++++++++------
2 files changed, 19 insertions(+), 6 deletions(-)
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 1feed71..5a53857 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -330,6 +330,7 @@ unifdef-y += scc.h
unifdef-y += sched.h
unifdef-y += screen_info.h
unifdef-y += sdla.h
+unifdef-y += securebits.h
unifdef-y += selinux_netlink.h
unifdef-y += sem.h
unifdef-y += serial_core.h
diff --git a/include/linux/securebits.h b/include/linux/securebits.h
index d2c5ed8..3340617 100644
--- a/include/linux/securebits.h
+++ b/include/linux/securebits.h
@@ -1,6 +1,15 @@
#ifndef _LINUX_SECUREBITS_H
#define _LINUX_SECUREBITS_H 1
+/* Each securesetting is implemented using two bits. One bit specifies
+ whether the setting is on or off. The other bit specify whether the
+ setting is locked or not. A setting which is locked cannot be
+ changed from user-level. */
+#define issecure_mask(X) (1 << (X))
+#ifdef __KERNEL__
+#define issecure(X) (issecure_mask(X) & current_cred_xxx(securebits))
+#endif
+
#define SECUREBITS_DEFAULT 0x00000000
/* When set UID 0 has no special privileges. When unset, we support
@@ -12,6 +21,9 @@
#define SECURE_NOROOT 0
#define SECURE_NOROOT_LOCKED 1 /* make bit-0 immutable */
+#define SECBIT_NOROOT (issecure_mask(SECURE_NOROOT))
+#define SECBIT_NOROOT_LOCKED (issecure_mask(SECURE_NOROOT_LOCKED))
+
/* When set, setuid to/from uid 0 does not trigger capability-"fixup".
When unset, to provide compatiblility with old programs relying on
set*uid to gain/lose privilege, transitions to/from uid 0 cause
@@ -19,6 +31,10 @@
#define SECURE_NO_SETUID_FIXUP 2
#define SECURE_NO_SETUID_FIXUP_LOCKED 3 /* make bit-2 immutable */
+#define SECBIT_NO_SETUID_FIXUP (issecure_mask(SECURE_NO_SETUID_FIXUP))
+#define SECBIT_NO_SETUID_FIXUP_LOCKED \
+ (issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED))
+
/* When set, a process can retain its capabilities even after
transitioning to a non-root user (the set-uid fixup suppressed by
bit 2). Bit-4 is cleared when a process calls exec(); setting both
@@ -27,12 +43,8 @@
#define SECURE_KEEP_CAPS 4
#define SECURE_KEEP_CAPS_LOCKED 5 /* make bit-4 immutable */
-/* Each securesetting is implemented using two bits. One bit specifies
- whether the setting is on or off. The other bit specify whether the
- setting is locked or not. A setting which is locked cannot be
- changed from user-level. */
-#define issecure_mask(X) (1 << (X))
-#define issecure(X) (issecure_mask(X) & current_cred_xxx(securebits))
+#define SECBIT_KEEP_CAPS (issecure_mask(SECURE_KEEP_CAPS))
+#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
#define SECURE_ALL_BITS (issecure_mask(SECURE_NOROOT) | \
issecure_mask(SECURE_NO_SETUID_FIXUP) | \
--
1.6.1
On Thu, 29 Oct 2009, Serge E. Hallyn wrote:
> Hi James, would you mind taking the following into
> security-testing?
Applied to
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6#next
>
> The securebits are used by passing them to prctl with the
> PR_{S,G}ET_SECUREBITS commands. But the defines must be
> shifted to be used in prctl, which begs to be confused and
> misused by userspace. So define some more convenient
> values for userspace to specify. This way userspace does
>
> prctl(PR_SET_SECUREBITS, SECBIT_NOROOT);
>
> instead of
>
> prctl(PR_SET_SECUREBITS, 1 << SECURE_NOROOT);
>
> (Thanks to Michael for the idea)
>
> This patch also adds include/linux/securebits to the installed headers.
> Then perhaps it can be included by glibc's sys/prctl.h.
>
> Changelog:
> Oct 29: Stephen Rothwell points out that issecure can
> be under __KERNEL__.
> Oct 14: (Suggestions by Michael Kerrisk):
> 1. spell out SETUID in SECBIT_NO_SETUID*
> 2. SECBIT_X_LOCKED does not imply SECBIT_X
> 3. add definitions for keepcaps
> Oct 14: As suggested by Michael Kerrisk, don't
> use SB_* as that convention is already in
> use. Use SECBIT_ prefix instead.
>
> Signed-off-by: Serge E. Hallyn <[email protected]>
> Acked-by: Andrew G. Morgan <[email protected]>
> Acked-by: Michael Kerrisk <[email protected]>
> Cc: Ulrich Drepper <[email protected]>
> Cc: James Morris <[email protected]>
> ---
> include/linux/Kbuild | 1 +
> include/linux/securebits.h | 24 ++++++++++++++++++------
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
> index 1feed71..5a53857 100644
> --- a/include/linux/Kbuild
> +++ b/include/linux/Kbuild
> @@ -330,6 +330,7 @@ unifdef-y += scc.h
> unifdef-y += sched.h
> unifdef-y += screen_info.h
> unifdef-y += sdla.h
> +unifdef-y += securebits.h
> unifdef-y += selinux_netlink.h
> unifdef-y += sem.h
> unifdef-y += serial_core.h
> diff --git a/include/linux/securebits.h b/include/linux/securebits.h
> index d2c5ed8..3340617 100644
> --- a/include/linux/securebits.h
> +++ b/include/linux/securebits.h
> @@ -1,6 +1,15 @@
> #ifndef _LINUX_SECUREBITS_H
> #define _LINUX_SECUREBITS_H 1
>
> +/* Each securesetting is implemented using two bits. One bit specifies
> + whether the setting is on or off. The other bit specify whether the
> + setting is locked or not. A setting which is locked cannot be
> + changed from user-level. */
> +#define issecure_mask(X) (1 << (X))
> +#ifdef __KERNEL__
> +#define issecure(X) (issecure_mask(X) & current_cred_xxx(securebits))
> +#endif
> +
> #define SECUREBITS_DEFAULT 0x00000000
>
> /* When set UID 0 has no special privileges. When unset, we support
> @@ -12,6 +21,9 @@
> #define SECURE_NOROOT 0
> #define SECURE_NOROOT_LOCKED 1 /* make bit-0 immutable */
>
> +#define SECBIT_NOROOT (issecure_mask(SECURE_NOROOT))
> +#define SECBIT_NOROOT_LOCKED (issecure_mask(SECURE_NOROOT_LOCKED))
> +
> /* When set, setuid to/from uid 0 does not trigger capability-"fixup".
> When unset, to provide compatiblility with old programs relying on
> set*uid to gain/lose privilege, transitions to/from uid 0 cause
> @@ -19,6 +31,10 @@
> #define SECURE_NO_SETUID_FIXUP 2
> #define SECURE_NO_SETUID_FIXUP_LOCKED 3 /* make bit-2 immutable */
>
> +#define SECBIT_NO_SETUID_FIXUP (issecure_mask(SECURE_NO_SETUID_FIXUP))
> +#define SECBIT_NO_SETUID_FIXUP_LOCKED \
> + (issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED))
> +
> /* When set, a process can retain its capabilities even after
> transitioning to a non-root user (the set-uid fixup suppressed by
> bit 2). Bit-4 is cleared when a process calls exec(); setting both
> @@ -27,12 +43,8 @@
> #define SECURE_KEEP_CAPS 4
> #define SECURE_KEEP_CAPS_LOCKED 5 /* make bit-4 immutable */
>
> -/* Each securesetting is implemented using two bits. One bit specifies
> - whether the setting is on or off. The other bit specify whether the
> - setting is locked or not. A setting which is locked cannot be
> - changed from user-level. */
> -#define issecure_mask(X) (1 << (X))
> -#define issecure(X) (issecure_mask(X) & current_cred_xxx(securebits))
> +#define SECBIT_KEEP_CAPS (issecure_mask(SECURE_KEEP_CAPS))
> +#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
>
> #define SECURE_ALL_BITS (issecure_mask(SECURE_NOROOT) | \
> issecure_mask(SECURE_NO_SETUID_FIXUP) | \
> --
> 1.6.1
>
--
James Morris
<[email protected]>
On Thu, Oct 29, 2009 at 10:51 PM, James Morris <[email protected]> wrote:
> On Thu, 29 Oct 2009, Serge E. Hallyn wrote:
>
>> Hi James, would you mind taking the following into
>> security-testing?
>
>
> Applied to
> git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6#next
It doesn't look like this change is in 2.6.32-rc7. Is it planned to
push this out for 2.6.32?
Cheers,
Michael
>> The securebits are used by passing them to prctl with the
>> PR_{S,G}ET_SECUREBITS commands. ?But the defines must be
>> shifted to be used in prctl, which begs to be confused and
>> misused by userspace. ?So define some more convenient
>> values for userspace to specify. ?This way userspace does
>>
>> ? ? ? prctl(PR_SET_SECUREBITS, SECBIT_NOROOT);
>>
>> instead of
>>
>> ? ? ? prctl(PR_SET_SECUREBITS, 1 << SECURE_NOROOT);
>>
>> (Thanks to Michael for the idea)
>>
>> This patch also adds include/linux/securebits to the installed headers.
>> Then perhaps it can be included by glibc's sys/prctl.h.
>>
>> Changelog:
>> ? ? ? Oct 29: Stephen Rothwell points out that issecure can
>> ? ? ? ? ? ? ? be under __KERNEL__.
>> ? ? ? Oct 14: (Suggestions by Michael Kerrisk):
>> ? ? ? ? ? ? ? 1. spell out SETUID in SECBIT_NO_SETUID*
>> ? ? ? ? ? ? ? 2. SECBIT_X_LOCKED does not imply SECBIT_X
>> ? ? ? ? ? ? ? 3. add definitions for keepcaps
>> ? ? ? ? Oct 14: As suggested by Michael Kerrisk, don't
>> ? ? ? ? ? ? ? use SB_* as that convention is already in
>> ? ? ? ? ? ? ? use. ?Use SECBIT_ prefix instead.
>>
>> Signed-off-by: Serge E. Hallyn <[email protected]>
>> Acked-by: Andrew G. Morgan <[email protected]>
>> Acked-by: Michael Kerrisk <[email protected]>
>> Cc: Ulrich Drepper <[email protected]>
>> Cc: James Morris <[email protected]>
>> ---
>> ?include/linux/Kbuild ? ? ? | ? ?1 +
>> ?include/linux/securebits.h | ? 24 ++++++++++++++++++------
>> ?2 files changed, 19 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
>> index 1feed71..5a53857 100644
>> --- a/include/linux/Kbuild
>> +++ b/include/linux/Kbuild
>> @@ -330,6 +330,7 @@ unifdef-y += scc.h
>> ?unifdef-y += sched.h
>> ?unifdef-y += screen_info.h
>> ?unifdef-y += sdla.h
>> +unifdef-y += securebits.h
>> ?unifdef-y += selinux_netlink.h
>> ?unifdef-y += sem.h
>> ?unifdef-y += serial_core.h
>> diff --git a/include/linux/securebits.h b/include/linux/securebits.h
>> index d2c5ed8..3340617 100644
>> --- a/include/linux/securebits.h
>> +++ b/include/linux/securebits.h
>> @@ -1,6 +1,15 @@
>> ?#ifndef _LINUX_SECUREBITS_H
>> ?#define _LINUX_SECUREBITS_H 1
>>
>> +/* Each securesetting is implemented using two bits. One bit specifies
>> + ? whether the setting is on or off. The other bit specify whether the
>> + ? setting is locked or not. A setting which is locked cannot be
>> + ? changed from user-level. */
>> +#define issecure_mask(X) ? ? (1 << (X))
>> +#ifdef __KERNEL__
>> +#define issecure(X) ? ? ? ? ?(issecure_mask(X) & current_cred_xxx(securebits))
>> +#endif
>> +
>> ?#define SECUREBITS_DEFAULT 0x00000000
>>
>> ?/* When set UID 0 has no special privileges. When unset, we support
>> @@ -12,6 +21,9 @@
>> ?#define SECURE_NOROOT ? ? ? ? ? ? ? ? ? ? ? ?0
>> ?#define SECURE_NOROOT_LOCKED ? ? ? ? 1 ?/* make bit-0 immutable */
>>
>> +#define SECBIT_NOROOT ? ? ? ? ? ? ? ?(issecure_mask(SECURE_NOROOT))
>> +#define SECBIT_NOROOT_LOCKED (issecure_mask(SECURE_NOROOT_LOCKED))
>> +
>> ?/* When set, setuid to/from uid 0 does not trigger capability-"fixup".
>> ? ? When unset, to provide compatiblility with old programs relying on
>> ? ? set*uid to gain/lose privilege, transitions to/from uid 0 cause
>> @@ -19,6 +31,10 @@
>> ?#define SECURE_NO_SETUID_FIXUP ? ? ? ? ? ? ? 2
>> ?#define SECURE_NO_SETUID_FIXUP_LOCKED ? ? ? ?3 ?/* make bit-2 immutable */
>>
>> +#define SECBIT_NO_SETUID_FIXUP ? ? ? (issecure_mask(SECURE_NO_SETUID_FIXUP))
>> +#define SECBIT_NO_SETUID_FIXUP_LOCKED \
>> + ? ? ? ? ? ? ? ? ? ? (issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED))
>> +
>> ?/* When set, a process can retain its capabilities even after
>> ? ? transitioning to a non-root user (the set-uid fixup suppressed by
>> ? ? bit 2). Bit-4 is cleared when a process calls exec(); setting both
>> @@ -27,12 +43,8 @@
>> ?#define SECURE_KEEP_CAPS ? ? ? ? ? ? 4
>> ?#define SECURE_KEEP_CAPS_LOCKED ? ? ? ? ? ? ?5 ?/* make bit-4 immutable */
>>
>> -/* Each securesetting is implemented using two bits. One bit specifies
>> - ? whether the setting is on or off. The other bit specify whether the
>> - ? setting is locked or not. A setting which is locked cannot be
>> - ? changed from user-level. */
>> -#define issecure_mask(X) ? ? (1 << (X))
>> -#define issecure(X) ? ? ? ? ?(issecure_mask(X) & current_cred_xxx(securebits))
>> +#define SECBIT_KEEP_CAPS ? ? (issecure_mask(SECURE_KEEP_CAPS))
>> +#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
>>
>> ?#define SECURE_ALL_BITS ? ? ? ? ? ? ?(issecure_mask(SECURE_NOROOT) | \
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?issecure_mask(SECURE_NO_SETUID_FIXUP) | \
>> --
>> 1.6.1
>>
>
> --
> James Morris
> <[email protected]>
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface" http://blog.man7.org/
On Sat, 14 Nov 2009, Michael Kerrisk wrote:
> On Thu, Oct 29, 2009 at 10:51 PM, James Morris <[email protected]> wrote:
> > On Thu, 29 Oct 2009, Serge E. Hallyn wrote:
> >
> >> Hi James, would you mind taking the following into
> >> security-testing?
> >
> >
> > Applied to
> > git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6#next
>
> It doesn't look like this change is in 2.6.32-rc7. Is it planned to
> push this out for 2.6.32?
No, this is being queued for the next kernel (2.6.33).
Currently, only fixes to regressions can be upstreamed for 2.6.32.
>
> Cheers,
>
> Michael
>
> >> The securebits are used by passing them to prctl with the
> >> PR_{S,G}ET_SECUREBITS commands. ?But the defines must be
> >> shifted to be used in prctl, which begs to be confused and
> >> misused by userspace. ?So define some more convenient
> >> values for userspace to specify. ?This way userspace does
> >>
> >> ? ? ? prctl(PR_SET_SECUREBITS, SECBIT_NOROOT);
> >>
> >> instead of
> >>
> >> ? ? ? prctl(PR_SET_SECUREBITS, 1 << SECURE_NOROOT);
> >>
> >> (Thanks to Michael for the idea)
> >>
> >> This patch also adds include/linux/securebits to the installed headers.
> >> Then perhaps it can be included by glibc's sys/prctl.h.
> >>
> >> Changelog:
> >> ? ? ? Oct 29: Stephen Rothwell points out that issecure can
> >> ? ? ? ? ? ? ? be under __KERNEL__.
> >> ? ? ? Oct 14: (Suggestions by Michael Kerrisk):
> >> ? ? ? ? ? ? ? 1. spell out SETUID in SECBIT_NO_SETUID*
> >> ? ? ? ? ? ? ? 2. SECBIT_X_LOCKED does not imply SECBIT_X
> >> ? ? ? ? ? ? ? 3. add definitions for keepcaps
> >> ? ? ? ? Oct 14: As suggested by Michael Kerrisk, don't
> >> ? ? ? ? ? ? ? use SB_* as that convention is already in
> >> ? ? ? ? ? ? ? use. ?Use SECBIT_ prefix instead.
> >>
> >> Signed-off-by: Serge E. Hallyn <[email protected]>
> >> Acked-by: Andrew G. Morgan <[email protected]>
> >> Acked-by: Michael Kerrisk <[email protected]>
> >> Cc: Ulrich Drepper <[email protected]>
> >> Cc: James Morris <[email protected]>
> >> ---
> >> ?include/linux/Kbuild ? ? ? | ? ?1 +
> >> ?include/linux/securebits.h | ? 24 ++++++++++++++++++------
> >> ?2 files changed, 19 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
> >> index 1feed71..5a53857 100644
> >> --- a/include/linux/Kbuild
> >> +++ b/include/linux/Kbuild
> >> @@ -330,6 +330,7 @@ unifdef-y += scc.h
> >> ?unifdef-y += sched.h
> >> ?unifdef-y += screen_info.h
> >> ?unifdef-y += sdla.h
> >> +unifdef-y += securebits.h
> >> ?unifdef-y += selinux_netlink.h
> >> ?unifdef-y += sem.h
> >> ?unifdef-y += serial_core.h
> >> diff --git a/include/linux/securebits.h b/include/linux/securebits.h
> >> index d2c5ed8..3340617 100644
> >> --- a/include/linux/securebits.h
> >> +++ b/include/linux/securebits.h
> >> @@ -1,6 +1,15 @@
> >> ?#ifndef _LINUX_SECUREBITS_H
> >> ?#define _LINUX_SECUREBITS_H 1
> >>
> >> +/* Each securesetting is implemented using two bits. One bit specifies
> >> + ? whether the setting is on or off. The other bit specify whether the
> >> + ? setting is locked or not. A setting which is locked cannot be
> >> + ? changed from user-level. */
> >> +#define issecure_mask(X) ? ? (1 << (X))
> >> +#ifdef __KERNEL__
> >> +#define issecure(X) ? ? ? ? ?(issecure_mask(X) & current_cred_xxx(securebits))
> >> +#endif
> >> +
> >> ?#define SECUREBITS_DEFAULT 0x00000000
> >>
> >> ?/* When set UID 0 has no special privileges. When unset, we support
> >> @@ -12,6 +21,9 @@
> >> ?#define SECURE_NOROOT ? ? ? ? ? ? ? ? ? ? ? ?0
> >> ?#define SECURE_NOROOT_LOCKED ? ? ? ? 1 ?/* make bit-0 immutable */
> >>
> >> +#define SECBIT_NOROOT ? ? ? ? ? ? ? ?(issecure_mask(SECURE_NOROOT))
> >> +#define SECBIT_NOROOT_LOCKED (issecure_mask(SECURE_NOROOT_LOCKED))
> >> +
> >> ?/* When set, setuid to/from uid 0 does not trigger capability-"fixup".
> >> ? ? When unset, to provide compatiblility with old programs relying on
> >> ? ? set*uid to gain/lose privilege, transitions to/from uid 0 cause
> >> @@ -19,6 +31,10 @@
> >> ?#define SECURE_NO_SETUID_FIXUP ? ? ? ? ? ? ? 2
> >> ?#define SECURE_NO_SETUID_FIXUP_LOCKED ? ? ? ?3 ?/* make bit-2 immutable */
> >>
> >> +#define SECBIT_NO_SETUID_FIXUP ? ? ? (issecure_mask(SECURE_NO_SETUID_FIXUP))
> >> +#define SECBIT_NO_SETUID_FIXUP_LOCKED \
> >> + ? ? ? ? ? ? ? ? ? ? (issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED))
> >> +
> >> ?/* When set, a process can retain its capabilities even after
> >> ? ? transitioning to a non-root user (the set-uid fixup suppressed by
> >> ? ? bit 2). Bit-4 is cleared when a process calls exec(); setting both
> >> @@ -27,12 +43,8 @@
> >> ?#define SECURE_KEEP_CAPS ? ? ? ? ? ? 4
> >> ?#define SECURE_KEEP_CAPS_LOCKED ? ? ? ? ? ? ?5 ?/* make bit-4 immutable */
> >>
> >> -/* Each securesetting is implemented using two bits. One bit specifies
> >> - ? whether the setting is on or off. The other bit specify whether the
> >> - ? setting is locked or not. A setting which is locked cannot be
> >> - ? changed from user-level. */
> >> -#define issecure_mask(X) ? ? (1 << (X))
> >> -#define issecure(X) ? ? ? ? ?(issecure_mask(X) & current_cred_xxx(securebits))
> >> +#define SECBIT_KEEP_CAPS ? ? (issecure_mask(SECURE_KEEP_CAPS))
> >> +#define SECBIT_KEEP_CAPS_LOCKED (issecure_mask(SECURE_KEEP_CAPS_LOCKED))
> >>
> >> ?#define SECURE_ALL_BITS ? ? ? ? ? ? ?(issecure_mask(SECURE_NOROOT) | \
> >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?issecure_mask(SECURE_NO_SETUID_FIXUP) | \
> >> --
> >> 1.6.1
> >>
> >
> > --
> > James Morris
> > <[email protected]>
> >
>
>
>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Author of "The Linux Programming Interface" http://blog.man7.org/
>
--
James Morris
<[email protected]>