From 59ec71575ab440cd5ca0aa53b2a2985b3639fad4 Mon Sep 17 00:00:00 2001 From: Alexey Gladkov Date: Mon, 29 Nov 2021 21:37:25 +0100 Subject: ucounts: Fix rlimit max values check The semantics of the rlimit max values differs from ucounts itself. When creating a new userns, we store the current rlimit of the process in ucount_max. Thus, the value of the limit in the parent userns is saved in the created one. The problem is that now we are taking the maximum value for counter from the same userns. So for init_user_ns it will always be RLIM_INFINITY. To fix the problem we need to check the counter value with the max value stored in userns. Reproducer: su - test -c "ulimit -u 3; sleep 5 & sleep 6 & unshare -U --map-root-user sh -c 'sleep 7 & sleep 8 & date; wait'" Before: [1] 175 [2] 176 Fri Nov 26 13:48:20 UTC 2021 [1]- Done sleep 5 [2]+ Done sleep 6 After: [1] 167 [2] 168 sh: fork: retry: Resource temporarily unavailable sh: fork: retry: Resource temporarily unavailable sh: fork: retry: Resource temporarily unavailable sh: fork: retry: Resource temporarily unavailable sh: fork: retry: Resource temporarily unavailable sh: fork: retry: Resource temporarily unavailable sh: fork: retry: Resource temporarily unavailable sh: fork: Interrupted system call [1]- Done sleep 5 [2]+ Done sleep 6 Fixes: c54b245d0118 ("Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace") Reported-by: Gleb Fotengauer-Malinovskiy Signed-off-by: "Eric W. Biederman" Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/024ec805f6e16896f0b23e094773790d171d2c1c.1638218242.git.legion@kernel.org Signed-off-by: Eric W. Biederman --- kernel/ucount.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/ucount.c b/kernel/ucount.c index 4f5613dac227..7b32c356ebc5 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -264,15 +264,16 @@ void dec_ucount(struct ucounts *ucounts, enum ucount_type type) long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) { struct ucounts *iter; + long max = LONG_MAX; long ret = 0; for (iter = ucounts; iter; iter = iter->ns->ucounts) { - long max = READ_ONCE(iter->ns->ucount_max[type]); long new = atomic_long_add_return(v, &iter->ucount[type]); if (new < 0 || new > max) ret = LONG_MAX; else if (iter == ucounts) ret = new; + max = READ_ONCE(iter->ns->ucount_max[type]); } return ret; } @@ -312,15 +313,16 @@ long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type) { /* Caller must hold a reference to ucounts */ struct ucounts *iter; + long max = LONG_MAX; long dec, ret = 0; for (iter = ucounts; iter; iter = iter->ns->ucounts) { - long max = READ_ONCE(iter->ns->ucount_max[type]); long new = atomic_long_add_return(1, &iter->ucount[type]); if (new < 0 || new > max) goto unwind; if (iter == ucounts) ret = new; + max = READ_ONCE(iter->ns->ucount_max[type]); /* * Grab an extra ucount reference for the caller when * the rlimit count was previously 0. @@ -339,15 +341,16 @@ unwind: return 0; } -bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long max) +bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long rlimit) { struct ucounts *iter; - if (get_ucounts_value(ucounts, type) > max) - return true; + long max = rlimit; + if (rlimit > LONG_MAX) + max = LONG_MAX; for (iter = ucounts; iter; iter = iter->ns->ucounts) { - max = READ_ONCE(iter->ns->ucount_max[type]); if (get_ucounts_value(iter, type) > max) return true; + max = READ_ONCE(iter->ns->ucount_max[type]); } return false; } -- cgit v1.2.3