From: Elena Reshetova <elena.reshetova@intel.com> To: mingo@redhat.com Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, tj@kernel.org, hannes@cmpxchg.org, lizefan@huawei.com, acme@kernel.org, alexander.shishkin@linux.intel.com, eparis@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, luto@kernel.org, keescook@chromium.org, tglx@linutronix.de, dvhart@infradead.org, ebiederm@xmission.com, linux-mm@kvack.org, axboe@kernel.dk, Elena Reshetova <elena.reshetova@intel.com> Subject: [PATCH 09/16] perf/ring_buffer: convert ring_buffer.refcount to refcount_t Date: Wed, 15 Nov 2017 16:03:33 +0200 [thread overview] Message-ID: <1510754620-27088-10-git-send-email-elena.reshetova@intel.com> (raw) In-Reply-To: <1510754620-27088-1-git-send-email-elena.reshetova@intel.com> atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable ring_buffer.refcount is used as pure reference counter. Convert it to refcount_t and fix up the operations. **Important note for maintainers: Some functions from refcount_t API defined in lib/refcount.c have different memory ordering guarantees than their atomic counterparts. The full comparison can be seen in https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon in state to be merged to the documentation tree. Normally the differences should not matter since refcount_t provides enough guarantees to satisfy the refcounting use cases, but in some rare cases it might matter. Please double check that you don't have some undocumented memory guarantees for this variable usage. For the ring_buffer.refcount it might make a difference in following places: - ring_buffer_get(): increment in refcount_inc_not_zero() only guarantees control dependency on success vs. fully ordered atomic counterpart - ring_buffer_put(): decrement in refcount_dec_and_test() only provides RELEASE ordering and control dependency on success vs. fully ordered atomic counterpart Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> --- kernel/events/core.c | 4 ++-- kernel/events/internal.h | 3 ++- kernel/events/ring_buffer.c | 2 +- 3 files changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 29c381f..3497c6a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5020,7 +5020,7 @@ struct ring_buffer *ring_buffer_get(struct perf_event *event) rcu_read_lock(); rb = rcu_dereference(event->rb); if (rb) { - if (!atomic_inc_not_zero(&rb->refcount)) + if (!refcount_inc_not_zero(&rb->refcount)) rb = NULL; } rcu_read_unlock(); @@ -5030,7 +5030,7 @@ struct ring_buffer *ring_buffer_get(struct perf_event *event) void ring_buffer_put(struct ring_buffer *rb) { - if (!atomic_dec_and_test(&rb->refcount)) + if (!refcount_dec_and_test(&rb->refcount)) return; WARN_ON_ONCE(!list_empty(&rb->event_list)); diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 09b1537..86c5c7f 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -4,13 +4,14 @@ #include <linux/hardirq.h> #include <linux/uaccess.h> +#include <linux/refcount.h> /* Buffer handling */ #define RING_BUFFER_WRITABLE 0x01 struct ring_buffer { - atomic_t refcount; + refcount_t refcount; struct rcu_head rcu_head; #ifdef CONFIG_PERF_USE_VMALLOC struct work_struct work; diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 141aa2c..de12d36 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -284,7 +284,7 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) else rb->overwrite = 1; - atomic_set(&rb->refcount, 1); + refcount_set(&rb->refcount, 1); INIT_LIST_HEAD(&rb->event_list); spin_lock_init(&rb->event_lock); -- 2.7.4
WARNING: multiple messages have this Message-ID (diff)
From: Elena Reshetova <elena.reshetova@intel.com> To: mingo@redhat.com Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, tj@kernel.org, hannes@cmpxchg.org, lizefan@huawei.com, acme@kernel.org, alexander.shishkin@linux.intel.com, eparis@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, luto@kernel.org, keescook@chromium.org, tglx@linutronix.de, dvhart@infradead.org, ebiederm@xmission.com, linux-mm@kvack.org, axboe@kernel.dk, Elena Reshetova <elena.reshetova@intel.com> Subject: [PATCH 09/16] perf/ring_buffer: convert ring_buffer.refcount to refcount_t Date: Wed, 15 Nov 2017 16:03:33 +0200 [thread overview] Message-ID: <1510754620-27088-10-git-send-email-elena.reshetova@intel.com> (raw) In-Reply-To: <1510754620-27088-1-git-send-email-elena.reshetova@intel.com> atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable ring_buffer.refcount is used as pure reference counter. Convert it to refcount_t and fix up the operations. **Important note for maintainers: Some functions from refcount_t API defined in lib/refcount.c have different memory ordering guarantees than their atomic counterparts. The full comparison can be seen in https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon in state to be merged to the documentation tree. Normally the differences should not matter since refcount_t provides enough guarantees to satisfy the refcounting use cases, but in some rare cases it might matter. Please double check that you don't have some undocumented memory guarantees for this variable usage. For the ring_buffer.refcount it might make a difference in following places: - ring_buffer_get(): increment in refcount_inc_not_zero() only guarantees control dependency on success vs. fully ordered atomic counterpart - ring_buffer_put(): decrement in refcount_dec_and_test() only provides RELEASE ordering and control dependency on success vs. fully ordered atomic counterpart Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> --- kernel/events/core.c | 4 ++-- kernel/events/internal.h | 3 ++- kernel/events/ring_buffer.c | 2 +- 3 files changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 29c381f..3497c6a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5020,7 +5020,7 @@ struct ring_buffer *ring_buffer_get(struct perf_event *event) rcu_read_lock(); rb = rcu_dereference(event->rb); if (rb) { - if (!atomic_inc_not_zero(&rb->refcount)) + if (!refcount_inc_not_zero(&rb->refcount)) rb = NULL; } rcu_read_unlock(); @@ -5030,7 +5030,7 @@ struct ring_buffer *ring_buffer_get(struct perf_event *event) void ring_buffer_put(struct ring_buffer *rb) { - if (!atomic_dec_and_test(&rb->refcount)) + if (!refcount_dec_and_test(&rb->refcount)) return; WARN_ON_ONCE(!list_empty(&rb->event_list)); diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 09b1537..86c5c7f 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -4,13 +4,14 @@ #include <linux/hardirq.h> #include <linux/uaccess.h> +#include <linux/refcount.h> /* Buffer handling */ #define RING_BUFFER_WRITABLE 0x01 struct ring_buffer { - atomic_t refcount; + refcount_t refcount; struct rcu_head rcu_head; #ifdef CONFIG_PERF_USE_VMALLOC struct work_struct work; diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 141aa2c..de12d36 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -284,7 +284,7 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) else rb->overwrite = 1; - atomic_set(&rb->refcount, 1); + refcount_set(&rb->refcount, 1); INIT_LIST_HEAD(&rb->event_list); spin_lock_init(&rb->event_lock); -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-11-15 14:09 UTC|newest] Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-11-15 14:03 [PATCH 00/16] v6 kernel core pieces refcount conversions Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 01/16] futex: convert futex_pi_state.refcount to refcount_t Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 02/16] sched: convert sighand_struct.count " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 03/16] sched: convert signal_struct.sigcnt " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 04/16] sched: convert user_struct.__count " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-17 0:16 ` Kees Cook 2017-11-17 0:16 ` Kees Cook 2017-11-15 14:03 ` [PATCH 05/16] sched: convert numa_group.refcount " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 06/16] sched/task_struct: convert task_struct.usage " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 07/16] sched/task_struct: convert task_struct.stack_refcount " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 08/16] perf: convert perf_event_context.refcount " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova [this message] 2017-11-15 14:03 ` [PATCH 09/16] perf/ring_buffer: convert ring_buffer.refcount " Elena Reshetova 2017-11-15 14:03 ` [PATCH 10/16] perf/ring_buffer: convert ring_buffer.aux_refcount " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 11/16] uprobes: convert uprobe.ref " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 14:03 ` [PATCH 12/16] nsproxy: convert nsproxy.count " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-15 16:36 ` Eric W. Biederman 2017-11-15 16:36 ` Eric W. Biederman 2017-11-15 16:36 ` Eric W. Biederman 2017-11-17 7:16 ` Reshetova, Elena 2017-11-17 7:16 ` Reshetova, Elena 2017-11-15 14:03 ` [PATCH 13/16] groups: convert group_info.usage " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-17 0:08 ` Kees Cook 2017-11-17 0:08 ` Kees Cook 2017-11-15 14:03 ` [PATCH 14/16] creds: convert cred.usage " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-17 0:14 ` Kees Cook 2017-11-17 0:14 ` Kees Cook 2017-11-15 14:03 ` [PATCH 15/16] kcov: convert kcov.refcount " Elena Reshetova 2017-11-15 14:03 ` Elena Reshetova 2017-11-17 0:10 ` Kees Cook 2017-11-17 0:10 ` Kees Cook 2017-11-15 14:03 ` [PATCH 16/16] bdi: convert bdi_writeback_congested.refcnt from atomic_t " Elena Reshetova 2018-12-05 1:06 ` [PATCH 00/16] v6 kernel core pieces refcount conversions Kees Cook
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=1510754620-27088-10-git-send-email-elena.reshetova@intel.com \ --to=elena.reshetova@intel.com \ --cc=acme@kernel.org \ --cc=akpm@linux-foundation.org \ --cc=alexander.shishkin@linux.intel.com \ --cc=arnd@arndb.de \ --cc=axboe@kernel.dk \ --cc=dvhart@infradead.org \ --cc=ebiederm@xmission.com \ --cc=eparis@redhat.com \ --cc=gregkh@linuxfoundation.org \ --cc=hannes@cmpxchg.org \ --cc=keescook@chromium.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-mm@kvack.org \ --cc=lizefan@huawei.com \ --cc=luto@kernel.org \ --cc=mingo@redhat.com \ --cc=peterz@infradead.org \ --cc=tglx@linutronix.de \ --cc=tj@kernel.org \ --cc=viro@zeniv.linux.org.uk \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.