| From | "Eric W. Biederman" <> | Date | Thu, 10 Feb 2022 20:13:22 -0600 | Subject | [PATCH 6/8] ucounts: Handle inc_rlimit_ucounts wrapping in fork |
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Move inc_rlimit_ucounts from copy_creds into copy_process immediately after copy_creds where it can be called exactly once. Test for and handle it when inc_rlimit_ucounts returns LONG_MAX indicating the count has wrapped.
This is good hygenine and fixes a theoretical bug. In practice PID_MAX_LIMIT is at most 2^22 so there is not a chance the number of processes would ever wrap even on an architecture with a 32bit long.
Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- kernel/cred.c | 2 -- kernel/fork.c | 2 ++ 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/cred.c b/kernel/cred.c index 229cff081167..96d5fd6ff26f 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -358,7 +358,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) kdebug("share_creds(%p{%d,%d})", p->cred, atomic_read(&p->cred->usage), read_cred_subscribers(p->cred)); - inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); return 0; } @@ -395,7 +394,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) #endif p->cred = p->real_cred = get_cred(new); - inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); alter_cred_subscribers(new, 2); validate_creds(new); return 0; diff --git a/kernel/fork.c b/kernel/fork.c index 6f62d37f3650..69333078259c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2026,6 +2026,8 @@ static __latent_entropy struct task_struct *copy_process( goto bad_fork_free; retval = -EAGAIN; + if (inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1) == LONG_MAX) + goto bad_fork_cleanup_count; if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) { if ((task_ucounts(p) != &init_ucounts) && !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) -- 2.29.2
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