coredump: warn about unsafe suid_dumpable / core_pattern combo

When suid_dumpable=2, detect unsafe core_pattern settings and warn when
they are seen.

Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alan Cox <alan@linux.intel.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 95aae3f9c036..5af8390e0fae 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -2002,17 +2002,17 @@ static void coredump_finish(struct mm_struct *mm)
 void set_dumpable(struct mm_struct *mm, int value)
 {
         switch (value) {
-        case 0:
+        case SUID_DUMPABLE_DISABLED:
                 clear_bit(MMF_DUMPABLE, &mm->flags);
                 smp_wmb();
                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
                 break;
-        case 1:
+        case SUID_DUMPABLE_ENABLED:
                 set_bit(MMF_DUMPABLE, &mm->flags);
                 smp_wmb();
                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
                 break;
-        case 2:
+        case SUID_DUMPABLE_SAFE:
                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
                 smp_wmb();
                 set_bit(MMF_DUMPABLE, &mm->flags);
@@ -2025,7 +2025,7 @@ static int __get_dumpable(unsigned long mm_flags)
         int ret;
 
         ret = mm_flags & MMF_DUMPABLE_MASK;
-        return (ret >= 2) ? 2 : ret;
+        return (ret > SUID_DUMPABLE_ENABLED) ? SUID_DUMPABLE_SAFE : ret;
 }
 
 int get_dumpable(struct mm_struct *mm)
@@ -2142,7 +2142,7 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
          * so we dump it as root in mode 2, and only into a controlled
          * environment (pipe handler or fully qualified path).
          */
-        if (__get_dumpable(cprm.mm_flags) == 2) {
+        if (__get_dumpable(cprm.mm_flags) == SUID_DUMPABLE_SAFE) {
                 /* Setuid core dump mode */
                 flag = O_EXCL;          /* Stop rewrite attacks */
                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */