[PATCH] setuid core dump

Add a new `suid_dumpable' sysctl:

This value can be used to query and set the core dump mode for setuid
or otherwise protected/tainted binaries. The modes are

0 - (default) - traditional behaviour.  Any process which has changed
    privilege levels or is execute only will not be dumped

1 - (debug) - all processes dump core when possible.  The core dump is
    owned by the current user and no security is applied.  This is intended
    for system debugging situations only.  Ptrace is unchecked.

2 - (suidsafe) - any binary which normally would not be dumped is dumped
    readable by root only.  This allows the end user to remove such a dump but
    not access it directly.  For security reasons core dumps in this mode will
    not overwrite one another or other files.  This mode is appropriate when
    adminstrators are attempting to debug problems in a normal environment.

(akpm:

> > +EXPORT_SYMBOL(suid_dumpable);
>
> EXPORT_SYMBOL_GPL?

No problem to me.

> >  	if (current->euid == current->uid && current->egid == current->gid)
> >  		current->mm->dumpable = 1;
>
> Should this be SUID_DUMP_USER?

Actually the feedback I had from last time was that the SUID_ defines
should go because its clearer to follow the numbers. They can go
everywhere (and there are lots of places where dumpable is tested/used
as a bool in untouched code)

> Maybe this should be renamed to `dump_policy' or something.  Doing that
> would help us catch any code which isn't using the #defines, too.

Fair comment. The patch was designed to be easy to maintain for Red Hat
rather than for merging. Changing that field would create a gigantic
diff because it is used all over the place.

)

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 7e736e201c46..c1e82c514443 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -69,6 +69,11 @@ extern void remove_arg_zero(struct linux_binprm *);
 extern int search_binary_handler(struct linux_binprm *,struct pt_regs *);
 extern int flush_old_exec(struct linux_binprm * bprm);
 
+extern int suid_dumpable;
+#define SUID_DUMP_DISABLE       0       /* No setuid dumping */
+#define SUID_DUMP_USER          1       /* Dump as user of process */
+#define SUID_DUMP_ROOT          2       /* Dump as root */
+
 /* Stack area protections */
 #define EXSTACK_DEFAULT   0     /* Whatever the arch defaults to */
 #define EXSTACK_DISABLE_X 1     /* Disable executable stacks */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b58afd97a180..901742f92389 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -246,7 +246,7 @@ struct mm_struct {
 
         unsigned long saved_auxv[42]; /* for /proc/PID/auxv */
 
-        unsigned dumpable:1;
+        unsigned dumpable:2;
         cpumask_t cpu_vm_mask;
 
         /* Architecture-specific MM context */
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index a17745c80a91..614e939c78a4 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -136,6 +136,7 @@ enum
         KERN_UNKNOWN_NMI_PANIC=66, /* int: unknown nmi panic flag */
         KERN_BOOTLOADER_TYPE=67, /* int: boot loader type */
         KERN_RANDOMIZE=68, /* int: randomize virtual address space */
+        KERN_SETUID_DUMPABLE=69, /* int: behaviour of dumps for setuid core */
 };