From cd8d860dcce906cd477be7d0648ba6f56a52eaa6 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Tue, 28 Feb 2017 11:32:22 -0500 Subject: jump_label: Fix anonymous union initialization Pre-4.6 gcc do not allow direct static initialization of members of anonymous structs/unions. After commit 3821fd35b58d ("jump_label: Reduce the size of struct static_key") STATIC_KEY_INIT_{TRUE|FALSE} definitions cannot be compiled with those older compilers. Placing initializers inside curved brackets works around this problem. Link: http://lkml.kernel.org/r/1488299542-30765-1-git-send-email-boris.ostrovsky@oracle.com Fixes: 3821fd35b58d ("jump_label: Reduce the size of struct static_key") Reviewed-by: Jason Baron Compiled-by: Chris Mason Signed-off-by: Boris Ostrovsky Signed-off-by: Steven Rostedt (VMware) --- include/linux/jump_label.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index 680c98b2f41c..a7f90117cf7d 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -166,10 +166,10 @@ extern void static_key_disable(struct static_key *key); */ #define STATIC_KEY_INIT_TRUE \ { .enabled = { 1 }, \ - .entries = (void *)JUMP_TYPE_TRUE } + { .entries = (void *)JUMP_TYPE_TRUE } } #define STATIC_KEY_INIT_FALSE \ { .enabled = { 0 }, \ - .entries = (void *)JUMP_TYPE_FALSE } + { .entries = (void *)JUMP_TYPE_FALSE } } #else /* !HAVE_JUMP_LABEL */ -- cgit v1.2.3 From b17ef2ed624aa7c1f68ed11acd16ecbf80fe01d7 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Thu, 2 Mar 2017 17:28:45 -0500 Subject: jump_label: Add comment about initialization order for anonymous unions Commit 3821fd35b58d ("jump_label: Reduce the size of struct static_key") broke old compilers that could not handle static initialization of anonymous unions. Boris fixed it with a patch that added brackets around the static initializer. But this creates a dependency between those initializers and the structure's order of its fields. Document this dependency in case new fields are added to struct static_key in the future. Noted-by: Boris Ostrovsky Suggested-by: Chris Mason Signed-off-by: Steven Rostedt (VMware) --- include/linux/jump_label.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux') diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index a7f90117cf7d..28e04a33535a 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -90,6 +90,13 @@ extern bool static_key_initialized; struct static_key { atomic_t enabled; /* + * Note: + * To make anonymous unions work with old compilers, the static + * initialization of them requires brackets. This creates a dependency + * on the order of the struct with the initializers. If any fields + * are added, STATIC_KEY_INIT_TRUE and STATIC_KEY_INIT_FALSE may need + * to be modified. + * * bit 0 => 1 if key is initially true * 0 if initially false * bit 1 => 1 if points to struct static_key_mod -- cgit v1.2.3 From 040757f738e13caaa9c5078bca79aa97e11dde88 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sun, 5 Mar 2017 15:03:22 -0600 Subject: ucount: Remove the atomicity from ucount->count Always increment/decrement ucount->count under the ucounts_lock. The increments are there already and moving the decrements there means the locking logic of the code is simpler. This simplification in the locking logic fixes a race between put_ucounts and get_ucounts that could result in a use-after-free because the count could go zero then be found by get_ucounts and then be freed by put_ucounts. A bug presumably this one was found by a combination of syzkaller and KASAN. JongWhan Kim reported the syzkaller failure and Dmitry Vyukov spotted the race in the code. Cc: stable@vger.kernel.org Fixes: f6b2db1a3e8d ("userns: Make the count of user namespaces per user") Reported-by: JongHwan Kim Reported-by: Dmitry Vyukov Reviewed-by: Andrei Vagin Signed-off-by: "Eric W. Biederman" --- include/linux/user_namespace.h | 2 +- kernel/ucount.c | 18 +++++++++++------- 2 files changed, 12 insertions(+), 8 deletions(-) (limited to 'include/linux') diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index be765234c0a2..32354b4b4b2b 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -72,7 +72,7 @@ struct ucounts { struct hlist_node node; struct user_namespace *ns; kuid_t uid; - atomic_t count; + int count; atomic_t ucount[UCOUNT_COUNTS]; }; diff --git a/kernel/ucount.c b/kernel/ucount.c index 62630a40ab3a..b4eeee03934f 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -144,7 +144,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) new->ns = ns; new->uid = uid; - atomic_set(&new->count, 0); + new->count = 0; spin_lock_irq(&ucounts_lock); ucounts = find_ucounts(ns, uid, hashent); @@ -155,8 +155,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) ucounts = new; } } - if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) + if (ucounts->count == INT_MAX) ucounts = NULL; + else + ucounts->count += 1; spin_unlock_irq(&ucounts_lock); return ucounts; } @@ -165,13 +167,15 @@ static void put_ucounts(struct ucounts *ucounts) { unsigned long flags; - if (atomic_dec_and_test(&ucounts->count)) { - spin_lock_irqsave(&ucounts_lock, flags); + spin_lock_irqsave(&ucounts_lock, flags); + ucounts->count -= 1; + if (!ucounts->count) hlist_del_init(&ucounts->node); - spin_unlock_irqrestore(&ucounts_lock, flags); + else + ucounts = NULL; + spin_unlock_irqrestore(&ucounts_lock, flags); - kfree(ucounts); - } + kfree(ucounts); } static inline bool atomic_inc_below(atomic_t *v, int u) -- cgit v1.2.3