5:45 p.m.
Bug description: When I add an audit watch on a file with no arguments, I
get perm=rwxa but on ia64, changes to the mode and context aren't
audited. I get audit records on i386 and x86_64.
(from https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=239887 )
The sanity check in audit_match_class() is wrong, AUDIT_BITMASK_SIZE is
64, providing space for 2048 syscalls in 64 * 32bit integers. The
comparison only supports 256 syscalls (sizeof __u32 is 4), and silently
returns "no match" for valid higher-numbered syscalls.
This breaks class-based audit for all syscalls on ia64 since on that
architecture syscall numbers start at 1024. It breaks some syscall audit
on other architectures also, for example __NR_fchmodat is 306 on x86.
I'd suggest adding a printk() in addition to returning 0 - you don't want
to silently ignore unknown or unsupported syscalls when auditing.
Signed-off-by: Klaus Weidner <klaus(a)atsec.com>
Followup discussion was on the linux-audit mailing list:
https://www.redhat.com/archives/linux-audit/2007-May/msg00030.html
Acked-by: Al Viro <viro(a)zeniv.linux.org.uk>
--- linux-2.6.18.i686/kernel/auditfilter.c.lspp.80 2007-05-11 17:06:08.000000000 -0500
+++ linux-2.6.18.i686/kernel/auditfilter.c 2007-05-11 17:09:37.000000000 -0500
@@ -306,7 +306,7 @@
int audit_match_class(int class, unsigned syscall)
{
- if (unlikely(syscall >= AUDIT_BITMASK_SIZE * sizeof(__u32)))
+ if (unlikely(syscall >= AUDIT_BITMASK_SIZE * 32))
return 0;
if (unlikely(class >= AUDIT_SYSCALL_CLASSES || !classes[class]))
return 0;
8:19 a.m.
On Wed, 16 May 2007 17:45:42 CDT, Klaus Weidner said:
Bug description: When I add an audit watch on a file with no
arguments, I
get perm=rwxa but on ia64, changes to the mode and context aren't
audited. I get audit records on i386 and x86_64.
(from https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=239887 )
The sanity check in audit_match_class() is wrong, AUDIT_BITMASK_SIZE is
64, providing space for 2048 syscalls in 64 * 32bit integers. The
comparison only supports 256 syscalls (sizeof __u32 is 4), and silently
returns "no match" for valid higher-numbered syscalls.
This breaks class-based audit for all syscalls on ia64 since on that
architecture syscall numbers start at 1024. It breaks some syscall audit
on other architectures also, for example __NR_fchmodat is 306 on x86.
I'd suggest adding a printk() in addition to returning 0 - you don't want
to silently ignore unknown or unsupported syscalls when auditing.
Make it rate-limited, so a program can't unintentionally spam your logs.
8:58 a.m.
On Thursday 17 May 2007 09:19, Valdis.Kletnieks(a)vt.edu wrote:
> I'd suggest adding a printk() in addition to returning 0 -
you don't want
> to silently ignore unknown or unsupported syscalls when auditing.
Make it rate-limited, so a program can't unintentionally spam your logs.
For this to happen, the syscall would have to be > 2048. I'd almost image
syscalls out of range in general...whether being auditing by class as in this
case or with a typical syscall rule is a problem. So, way back over at
syscall entry would be the time to notice this problem instead of here. If we
are concerned about this, it might be a general control feature like
enable/disable, fail mode, or backlog. We could make something to report out
of range syscalls.
-Steve
10:23 a.m.
On Thu, May 17, 2007 at 09:58:25AM -0400, Steve Grubb wrote:
On Thursday 17 May 2007 09:19, Valdis.Kletnieks(a)vt.edu wrote:
> > I'd suggest adding a printk() in addition to returning 0 - you don't
want
> > to silently ignore unknown or unsupported syscalls when auditing.
>
> Make it rate-limited, so a program can't unintentionally spam your logs.
For this to happen, the syscall would have to be > 2048. I'd almost image
syscalls out of range in general...whether being auditing by class as in this
case or with a typical syscall rule is a problem. So, way back over at
syscall entry would be the time to notice this problem instead of here. If we
are concerned about this, it might be a general control feature like
enable/disable, fail mode, or backlog. We could make something to report out
of range syscalls.
Can we agree to do just the simple fix for this issue for now, and maybe
revisit adding additional sanity checks later if people think they are
helpful?
-Klaus
10:45 a.m.
On Thursday 17 May 2007 11:23, Klaus Weidner wrote:
> So, way back over at syscall entry would be the time to notice
this
> problem instead of here. If we are concerned about this, it might be a
> general control feature like enable/disable, fail mode, or backlog. We
> could make something to report out of range syscalls.
Can we agree to do just the simple fix for this issue for now, and maybe
revisit adding additional sanity checks later if people think they are
helpful?
Certainly. The patch as submitted is fine and Al ack'ed it. I was thinking we
should have one more cleanup as a separate patch at some point that catches
this at syscall entry and allows ignore/printk/panic selection just like the
fail option for the audit system does. In the case of ignore (which would be
default), your patch is needed.
-Steve
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4 comments
3 participants
participants (3)
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Klaus Weidner -
Steve Grubb -
Valdis.Kletnieks＠vt.edu