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authorKees Cook <keescook@chromium.org>2012-07-30 14:39:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-30 17:25:11 -0700
commit54b501992dd2a839e94e76aa392c392b55080ce8 (patch)
tree6d174fb95516f01e385d31d5ef87a248d8740fd2
parent9520628e8ceb69fa9a4aee6b57f22675d9e1b709 (diff)
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>
-rw-r--r--fs/exec.c10
-rw-r--r--include/linux/sched.h5
-rw-r--r--kernel/sysctl.c37
3 files changed, 45 insertions, 7 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 */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a721cef7e2d4..1e26a5e45aa6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -406,6 +406,11 @@ static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
extern void set_dumpable(struct mm_struct *mm, int value);
extern int get_dumpable(struct mm_struct *mm);
+/* get/set_dumpable() values */
+#define SUID_DUMPABLE_DISABLED 0
+#define SUID_DUMPABLE_ENABLED 1
+#define SUID_DUMPABLE_SAFE 2
+
/* mm flags */
/* dumpable bits */
#define MMF_DUMPABLE 0 /* core dump is permitted */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4ab11879aeb4..b46f496405e4 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -174,6 +174,11 @@ static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
#endif
+static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+static int proc_dostring_coredump(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+
#ifdef CONFIG_MAGIC_SYSRQ
/* Note: sysrq code uses it's own private copy */
static int __sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
@@ -410,7 +415,7 @@ static struct ctl_table kern_table[] = {
.data = core_pattern,
.maxlen = CORENAME_MAX_SIZE,
.mode = 0644,
- .proc_handler = proc_dostring,
+ .proc_handler = proc_dostring_coredump,
},
{
.procname = "core_pipe_limit",
@@ -1498,7 +1503,7 @@ static struct ctl_table fs_table[] = {
.data = &suid_dumpable,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
+ .proc_handler = proc_dointvec_minmax_coredump,
.extra1 = &zero,
.extra2 = &two,
},
@@ -2009,6 +2014,34 @@ int proc_dointvec_minmax(struct ctl_table *table, int write,
do_proc_dointvec_minmax_conv, &param);
}
+static void validate_coredump_safety(void)
+{
+ if (suid_dumpable == SUID_DUMPABLE_SAFE &&
+ core_pattern[0] != '/' && core_pattern[0] != '|') {
+ printk(KERN_WARNING "Unsafe core_pattern used with "\
+ "suid_dumpable=2. Pipe handler or fully qualified "\
+ "core dump path required.\n");
+ }
+}
+
+static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (!error)
+ validate_coredump_safety();
+ return error;
+}
+
+static int proc_dostring_coredump(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int error = proc_dostring(table, write, buffer, lenp, ppos);
+ if (!error)
+ validate_coredump_safety();
+ return error;
+}
+
static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int write,
void __user *buffer,
size_t *lenp, loff_t *ppos,