Re: [PATCH v4 2/3] audit: add support for the openat2 syscall

On Tue, Feb 8, 2022 at 10:44 PM Jeff Mahoney <jeffm(a)suse.com&gt; wrote: > > Hi Richard - > > On 5/19/21 16:00, Richard Guy Briggs wrote: > > The openat2(2) syscall was added in kernel v5.6 with commit fddb5d430ad9 > > ("open: introduce openat2(2) syscall") > > > > Add the openat2(2) syscall to the audit syscall classifier. > > > > Link: https://github.com/linux-audit/audit-kernel/issues/67 > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > Link: https://lore.kernel.org/r/f5f1a4d8699613f8c02ce762807228c841c2e26f.162136... > > --- > > [...] > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > > index d775ea16505b..3f59ab209dfd 100644 > > --- a/kernel/auditsc.c > > +++ b/kernel/auditsc.c > > @@ -76,6 +76,7 @@ > > #include <linux/fsnotify_backend.h> > > #include <uapi/linux/limits.h> > > #include <uapi/linux/netfilter/nf_tables.h> > > +#include <uapi/linux/openat2.h> > > > > #include "audit.h" > > > > @@ -196,6 +197,8 @@ static int audit_match_perm(struct audit_context *ctx, int mask) > > return ((mask & AUDIT_PERM_WRITE) && ctx->argv[0] == SYS_BIND); > > case AUDITSC_EXECVE: > > return mask & AUDIT_PERM_EXEC; > > + case AUDITSC_OPENAT2: > > + return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags); > > default: > > return 0; > > } > > ctx->argv[2] holds a userspace pointer and can't be dereferenced like this. > > I'm getting oopses, like so: > BUG: unable to handle page fault for address: 00007fff961bbe70 Thanks Jeff. Yes, this is obviously the wrong thing to being doing; I remember checking to make sure we placed the audit_openat2_how() hook after the open_how was copied from userspace, but I missed the argv dereference in the syscall exit path when reviewing the code. Richard, as we are already copying the open_how info into audit_context::openat2 safely, the obvious fix is to convert audit_match_perm() to use the previously copied value instead of argv. If you can't submit a patch for this today please let me know.