summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
-rw-r--r--fs/exec.c17
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/cred.c6
-rw-r--r--kernel/fork.c1
-rw-r--r--kernel/sys.c15
5 files changed, 32 insertions, 8 deletions
diff --git a/fs/exec.c b/fs/exec.c
index da80612..25dcbe5 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1459,6 +1459,23 @@ static int do_execve_common(const char *filename,
struct files_struct *displaced;
bool clear_in_exec;
int retval;
+ const struct cred *cred = current_cred();
+
+ /*
+ * We move the actual failure in case of RLIMIT_NPROC excess from
+ * set*uid() to execve() because too many poorly written programs
+ * don't check setuid() return code. Here we additionally recheck
+ * whether NPROC limit is still exceeded.
+ */
+ if ((current->flags & PF_NPROC_EXCEEDED) &&
+ atomic_read(&cred->user->processes) > rlimit(RLIMIT_NPROC)) {
+ retval = -EAGAIN;
+ goto out_ret;
+ }
+
+ /* We're below the limit (still or again), so we don't want to make
+ * further execve() calls fail. */
+ current->flags &= ~PF_NPROC_EXCEEDED;
retval = unshare_files(&displaced);
if (retval)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 20b03bf..4ac2c05 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1767,6 +1767,7 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
#define PF_DUMPCORE 0x00000200 /* dumped core */
#define PF_SIGNALED 0x00000400 /* killed by a signal */
#define PF_MEMALLOC 0x00000800 /* Allocating memory */
+#define PF_NPROC_EXCEEDED 0x00001000 /* set_user noticed that RLIMIT_NPROC was exceeded */
#define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
#define PF_FREEZING 0x00004000 /* freeze in progress. do not account to load */
#define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
diff --git a/kernel/cred.c b/kernel/cred.c
index 174fa84..8ef31f5 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -508,10 +508,8 @@ int commit_creds(struct cred *new)
key_fsgid_changed(task);
/* do it
- * - What if a process setreuid()'s and this brings the
- * new uid over his NPROC rlimit? We can check this now
- * cheaply with the new uid cache, so if it matters
- * we should be checking for it. -DaveM
+ * RLIMIT_NPROC limits on user->processes have already been checked
+ * in set_user().
*/
alter_cred_subscribers(new, 2);
if (new->user != old->user)
diff --git a/kernel/fork.c b/kernel/fork.c
index e7ceaca..8e6b6f4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1111,6 +1111,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->real_cred->user != INIT_USER)
goto bad_fork_free;
}
+ current->flags &= ~PF_NPROC_EXCEEDED;
retval = copy_creds(p, clone_flags);
if (retval < 0)
diff --git a/kernel/sys.c b/kernel/sys.c
index a101ba3..dd948a1 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -621,11 +621,18 @@ static int set_user(struct cred *new)
if (!new_user)
return -EAGAIN;
+ /*
+ * We don't fail in case of NPROC limit excess here because too many
+ * poorly written programs don't check set*uid() return code, assuming
+ * it never fails if called by root. We may still enforce NPROC limit
+ * for programs doing set*uid()+execve() by harmlessly deferring the
+ * failure to the execve() stage.
+ */
if (atomic_read(&new_user->processes) >= rlimit(RLIMIT_NPROC) &&
- new_user != INIT_USER) {
- free_uid(new_user);
- return -EAGAIN;
- }
+ new_user != INIT_USER)
+ current->flags |= PF_NPROC_EXCEEDED;
+ else
+ current->flags &= ~PF_NPROC_EXCEEDED;
free_uid(new->user);
new->user = new_user;
OpenPOWER on IntegriCloud