WIP: only remove non-dumpable in the non-suid program

[Willy Tarreau]

this way sudo doesn't drop its own not-dumpable flag before executing.
---
 fs/coredump.c                  |  2 ++
 include/linux/sched/coredump.h |  4 ++--
 kernel/sys.c                   | 15 ++++++++++-----
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 3224dee44d30..5f0bfe2c00a6 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -609,6 +609,8 @@ void do_coredump(const kernel_siginfo_t *siginfo)
 		goto fail;
 	if (!__get_dumpable(cprm.mm_flags))
 		goto fail;
+	if (cprm.mm_flags & MMF_NOT_DUMPABLE_MASK)
+		goto fail;
 
 	cred = prepare_creds();
 	if (!cred)
diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h
index 302f31247c90..662508d139e1 100644
--- a/include/linux/sched/coredump.h
+++ b/include/linux/sched/coredump.h
@@ -80,8 +80,8 @@ extern void set_dumpable(struct mm_struct *mm, int value);
  */
 static inline int __get_dumpable(unsigned long mm_flags)
 {
-	if (mm_flags & MMF_NOT_DUMPABLE_MASK)
-		return SUID_DUMP_DISABLE;
+	//if (mm_flags & MMF_NOT_DUMPABLE_MASK)
+	//	return SUID_DUMP_DISABLE;
 	return mm_flags & MMF_DUMPABLE_MASK;
 }
 
diff --git a/kernel/sys.c b/kernel/sys.c
index f4405e004145..0ecdb4cc64e7 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -564,7 +564,8 @@ long __sys_setreuid(uid_t ruid, uid_t euid)
 		goto error;
 
 	/* attempt to change ID drops the not-dumpable protection */
-	clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
+	if (get_dumpable(current->mm))
+		clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
 
 	return commit_creds(new);
 
@@ -629,7 +630,8 @@ long __sys_setuid(uid_t uid)
 		goto error;
 
 	/* attempt to change ID drops the not-dumpable protection */
-	clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
+	if (get_dumpable(current->mm))
+		clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
 
 	return commit_creds(new);
 
@@ -711,7 +713,8 @@ long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
 		goto error;
 
 	/* attempt to change ID drops the not-dumpable protection */
-	clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
+	if (get_dumpable(current->mm))
+		clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
 
 	return commit_creds(new);
 
@@ -1225,7 +1228,8 @@ int ksys_setsid(void)
 	write_unlock_irq(&tasklist_lock);
 	if (err > 0) {
 		/* session leaders reset the not-dumpable protection */
-		clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
+		if (get_dumpable(current->mm))
+			clear_bit(MMF_NOT_DUMPABLE, &current->mm->flags);
 
 		proc_sid_connector(group_leader);
 		sched_autogroup_create_attach(group_leader);
@@ -1627,7 +1631,8 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
 	 * If an application wants to change its own core dump settings, it
 	 * wants to decide on its dumpability so we reset MMF_NOT_DUMPABLE.
 	 */
-	if (!retval && new_rlim && resource == RLIMIT_CORE && tsk == current)
+	if (!retval && new_rlim && resource == RLIMIT_CORE && tsk == current &&
+	    get_dumpable(tsk->mm))
 		clear_bit(MMF_NOT_DUMPABLE, &tsk->mm->flags);
 out:
 	read_unlock(&tasklist_lock);
-- 
2.17.5


--qMm9M+Fa2AknHoGS
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename="0002-WIP-only-change-not_dumpable-via-prctl-and-setrlimit.patch"