From a76a82a3e38c8d3fb6499e3dfaeb0949241ab588 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 26 Jan 2017 16:39:55 +0100 Subject: perf/core: Fix use-after-free bug Dmitry reported a KASAN use-after-free on event->group_leader. It turns out there's a hole in perf_remove_from_context() due to event_function_call() not calling its function when the task associated with the event is already dead. In this case the event will have been detached from the task, but the grouping will have been retained, such that group operations might still work properly while there are live child events etc. This does however mean that we can miss a perf_group_detach() call when the group decomposes, this in turn can then lead to use-after-free. Fix it by explicitly doing the group detach if its still required. Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Mathieu Desnoyers Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org # v4.5+ Cc: syzkaller Fixes: 63b6da39bb38 ("perf: Fix perf_event_exit_task() race") Link: http://lkml.kernel.org/r/20170126153955.GD6515@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/events/core.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/events/core.c b/kernel/events/core.c index 110b38a..4e1f4c0 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1469,7 +1469,6 @@ ctx_group_list(struct perf_event *event, struct perf_event_context *ctx) static void list_add_event(struct perf_event *event, struct perf_event_context *ctx) { - lockdep_assert_held(&ctx->lock); WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT); @@ -1624,6 +1623,8 @@ static void perf_group_attach(struct perf_event *event) { struct perf_event *group_leader = event->group_leader, *pos; + lockdep_assert_held(&event->ctx->lock); + /* * We can have double attach due to group movement in perf_event_open. */ @@ -1697,6 +1698,8 @@ static void perf_group_detach(struct perf_event *event) struct perf_event *sibling, *tmp; struct list_head *list = NULL; + lockdep_assert_held(&event->ctx->lock); + /* * We can have double detach due to exit/hot-unplug + close. */ @@ -1895,9 +1898,29 @@ __perf_remove_from_context(struct perf_event *event, */ static void perf_remove_from_context(struct perf_event *event, unsigned long flags) { - lockdep_assert_held(&event->ctx->mutex); + struct perf_event_context *ctx = event->ctx; + + lockdep_assert_held(&ctx->mutex); event_function_call(event, __perf_remove_from_context, (void *)flags); + + /* + * The above event_function_call() can NO-OP when it hits + * TASK_TOMBSTONE. In that case we must already have been detached + * from the context (by perf_event_exit_event()) but the grouping + * might still be in-tact. + */ + WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT); + if ((flags & DETACH_GROUP) && + (event->attach_state & PERF_ATTACH_GROUP)) { + /* + * Since in that case we cannot possibly be scheduled, simply + * detach now. + */ + raw_spin_lock_irq(&ctx->lock); + perf_group_detach(event); + raw_spin_unlock_irq(&ctx->lock); + } } /* -- cgit v1.1 From 0b3589be9b98994ce3d5aeca52445d1f5627c4ba Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 26 Jan 2017 23:15:08 +0100 Subject: perf/core: Fix PERF_RECORD_MMAP2 prot/flags for anonymous memory Andres reported that MMAP2 records for anonymous memory always have their protection field 0. Turns out, someone daft put the prot/flags generation code in the file branch, leaving them unset for anonymous memory. Reported-by: Andres Freund Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Don Zickus Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Stephane Eranian Cc: Thomas Gleixner Cc: acme@kernel.org Cc: anton@ozlabs.org Cc: namhyung@kernel.org Cc: stable@vger.kernel.org # v3.16+ Fixes: f972eb63b100 ("perf: Pass protection and flags bits through mmap2 interface") Link: http://lkml.kernel.org/r/20170126221508.GF6536@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/events/core.c | 42 +++++++++++++++++++++--------------------- 1 file changed, 21 insertions(+), 21 deletions(-) (limited to 'kernel') diff --git a/kernel/events/core.c b/kernel/events/core.c index 4e1f4c0..e5aaa80 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6632,6 +6632,27 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) char *buf = NULL; char *name; + if (vma->vm_flags & VM_READ) + prot |= PROT_READ; + if (vma->vm_flags & VM_WRITE) + prot |= PROT_WRITE; + if (vma->vm_flags & VM_EXEC) + prot |= PROT_EXEC; + + if (vma->vm_flags & VM_MAYSHARE) + flags = MAP_SHARED; + else + flags = MAP_PRIVATE; + + if (vma->vm_flags & VM_DENYWRITE) + flags |= MAP_DENYWRITE; + if (vma->vm_flags & VM_MAYEXEC) + flags |= MAP_EXECUTABLE; + if (vma->vm_flags & VM_LOCKED) + flags |= MAP_LOCKED; + if (vma->vm_flags & VM_HUGETLB) + flags |= MAP_HUGETLB; + if (file) { struct inode *inode; dev_t dev; @@ -6658,27 +6679,6 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) maj = MAJOR(dev); min = MINOR(dev); - if (vma->vm_flags & VM_READ) - prot |= PROT_READ; - if (vma->vm_flags & VM_WRITE) - prot |= PROT_WRITE; - if (vma->vm_flags & VM_EXEC) - prot |= PROT_EXEC; - - if (vma->vm_flags & VM_MAYSHARE) - flags = MAP_SHARED; - else - flags = MAP_PRIVATE; - - if (vma->vm_flags & VM_DENYWRITE) - flags |= MAP_DENYWRITE; - if (vma->vm_flags & VM_MAYEXEC) - flags |= MAP_EXECUTABLE; - if (vma->vm_flags & VM_LOCKED) - flags |= MAP_LOCKED; - if (vma->vm_flags & VM_HUGETLB) - flags |= MAP_HUGETLB; - goto got_name; } else { if (vma->vm_ops && vma->vm_ops->name) { -- cgit v1.1