[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>

2 files changed, 20 insertions, 11 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index f006632c2ba7..0a2c8cda9638 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -525,7 +525,7 @@ asmlinkage long sys_setregid(gid_t rgid, gid_t egid)
         }
         if (new_egid != old_egid)
         {
-                current->mm->dumpable = 0;
+                current->mm->dumpable = suid_dumpable;
                 smp_wmb();
         }
         if (rgid != (gid_t) -1 ||
@@ -556,7 +556,7 @@ asmlinkage long sys_setgid(gid_t gid)
         {
                 if(old_egid != gid)
                 {
-                        current->mm->dumpable=0;
+                        current->mm->dumpable = suid_dumpable;
                         smp_wmb();
                 }
                 current->gid = current->egid = current->sgid = current->fsgid = gid;
@@ -565,7 +565,7 @@ asmlinkage long sys_setgid(gid_t gid)
         {
                 if(old_egid != gid)
                 {
-                        current->mm->dumpable=0;
+                        current->mm->dumpable = suid_dumpable;
                         smp_wmb();
                 }
                 current->egid = current->fsgid = gid;
@@ -596,7 +596,7 @@ static int set_user(uid_t new_ruid, int dumpclear)
 
         if(dumpclear)
         {
-                current->mm->dumpable = 0;
+                current->mm->dumpable = suid_dumpable;
                 smp_wmb();
         }
         current->uid = new_ruid;
@@ -653,7 +653,7 @@ asmlinkage long sys_setreuid(uid_t ruid, uid_t euid)
 
         if (new_euid != old_euid)
         {
-                current->mm->dumpable=0;
+                current->mm->dumpable = suid_dumpable;
                 smp_wmb();
         }
         current->fsuid = current->euid = new_euid;
@@ -703,7 +703,7 @@ asmlinkage long sys_setuid(uid_t uid)
 
         if (old_euid != uid)
         {
-                current->mm->dumpable = 0;
+                current->mm->dumpable = suid_dumpable;
                 smp_wmb();
         }
         current->fsuid = current->euid = uid;
@@ -748,7 +748,7 @@ asmlinkage long sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
         if (euid != (uid_t) -1) {
                 if (euid != current->euid)
                 {
-                        current->mm->dumpable = 0;
+                        current->mm->dumpable = suid_dumpable;
                         smp_wmb();
                 }
                 current->euid = euid;
@@ -798,7 +798,7 @@ asmlinkage long sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
         if (egid != (gid_t) -1) {
                 if (egid != current->egid)
                 {
-                        current->mm->dumpable = 0;
+                        current->mm->dumpable = suid_dumpable;
                         smp_wmb();
                 }
                 current->egid = egid;
@@ -845,7 +845,7 @@ asmlinkage long sys_setfsuid(uid_t uid)
         {
                 if (uid != old_fsuid)
                 {
-                        current->mm->dumpable = 0;
+                        current->mm->dumpable = suid_dumpable;
                         smp_wmb();
                 }
                 current->fsuid = uid;
@@ -875,7 +875,7 @@ asmlinkage long sys_setfsgid(gid_t gid)
         {
                 if (gid != old_fsgid)
                 {
-                        current->mm->dumpable = 0;
+                        current->mm->dumpable = suid_dumpable;
                         smp_wmb();
                 }
                 current->fsgid = gid;
@@ -1652,7 +1652,7 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
                                 error = 1;
                         break;
                 case PR_SET_DUMPABLE:
-                        if (arg2 != 0 && arg2 != 1) {
+                        if (arg2 < 0 || arg2 > 2) {
                                 error = -EINVAL;
                                 break;
                         }
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 701d12c63068..24a4d12d5aa9 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -58,6 +58,7 @@ extern int sysctl_overcommit_ratio;
 extern int max_threads;
 extern int sysrq_enabled;
 extern int core_uses_pid;
+extern int suid_dumpable;
 extern char core_pattern[];
 extern int cad_pid;
 extern int pid_max;
@@ -950,6 +951,14 @@ static ctl_table fs_table[] = {
                 .proc_handler   = &proc_dointvec,
         },
 #endif
+        {
+                .ctl_name       = KERN_SETUID_DUMPABLE,
+                .procname       = "suid_dumpable",
+                .data           = &suid_dumpable,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
         { .ctl_name = 0 }
 };