ucounts: Move RLIMIT_NPROC handling after set_user

During set*id() which cred->ucounts to charge the the current process
to is not known until after set_cred_ucounts.  So move the
RLIMIT_NPROC checking into a new helper flag_nproc_exceeded and call
flag_nproc_exceeded after set_cred_ucounts.

This is very much an arbitrary subset of the places where we currently
change the RLIMIT_NPROC accounting, designed to preserve the existing
logic.

Fixing the existing logic will be the subject of another series of
changes.

Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220216155832.680775-4-ebiederm@xmission.com
Fixes: 96a6f980d813 ("Reimplement RLIMIT_NPROC on top of ucounts")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/kernel/sys.c b/kernel/sys.c
index 8dd938a3d2bff74fc9d6447f6783655312d2c80d..97dc9e5d6bf92ca7e18c8f474d926e8c51d46679 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -472,6 +472,16 @@ static int set_user(struct cred *new)
        if (!new_user)
                return -EAGAIN;
 
+       free_uid(new->user);
+       new->user = new_user;
+       return 0;
+}
+
+static void flag_nproc_exceeded(struct cred *new)
+{
+       if (new->ucounts == current_ucounts())
+               return;
+
        /*
         * 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
@@ -480,14 +490,10 @@ static int set_user(struct cred *new)
         * failure to the execve() stage.
         */
        if (is_ucounts_overlimit(new->ucounts, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)) &&
-                       new_user != INIT_USER)
+                       new->user != INIT_USER)
                current->flags |= PF_NPROC_EXCEEDED;
        else
                current->flags &= ~PF_NPROC_EXCEEDED;
-
-       free_uid(new->user);
-       new->user = new_user;
-       return 0;
 }
 
 /*
@@ -562,6 +568,7 @@ long __sys_setreuid(uid_t ruid, uid_t euid)
        if (retval < 0)
                goto error;
 
+       flag_nproc_exceeded(new);
        return commit_creds(new);
 
 error:
@@ -624,6 +631,7 @@ long __sys_setuid(uid_t uid)
        if (retval < 0)
                goto error;
 
+       flag_nproc_exceeded(new);
        return commit_creds(new);
 
 error:
@@ -703,6 +711,7 @@ long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
        if (retval < 0)
                goto error;
 
+       flag_nproc_exceeded(new);
        return commit_creds(new);
 
 error: