linux/kernel/trace, branch v5.6

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

2020-03-13T18:13:45Z

Alexei Starovoitov says: ==================== pull-request: bpf 2020-03-12 The following pull-request contains BPF updates for your *net* tree. We've added 12 non-merge commits during the last 8 day(s) which contain a total of 12 files changed, 161 insertions(+), 15 deletions(-). The main changes are: 1) Andrii fixed two bugs in cgroup-bpf. 2) John fixed sockmap. 3) Luke fixed x32 jit. 4) Martin fixed two issues in struct_ops. 5) Yonghong fixed bpf_send_signal. 6) Yoshiki fixed BTF enum. ==================== Signed-off-by: David S. Miller

Merge tag 'trace-v5.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2020-03-11T16:54:59Z

Pull ftrace fix from Steven Rostedt: "Have ftrace lookup_rec() return a consistent record otherwise it can break live patching" * tag 'trace-v5.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: ftrace: Return the first found result in lookup_rec()

ftrace: Return the first found result in lookup_rec()

2020-03-11T14:37:12Z

It appears that ip ranges can overlap so. In that case lookup_rec() returns whatever results it got last even if it found nothing in last searched page. This breaks an obscure livepatch late module patching usecase: - load livepatch - load the patched module - unload livepatch - try to load livepatch again To fix this return from lookup_rec() as soon as it found the record containing searched-for ip. This used to be this way prior lookup_rec() introduction. Link: http://lkml.kernel.org/r/20200306174317.21699-1-asavkov@redhat.com Cc: stable@vger.kernel.org Fixes: 7e16f581a817 ("ftrace: Separate out functionality from ftrace_location_range()") Signed-off-by: Artem Savkov Signed-off-by: Steven Rostedt (VMware)

Merge tag 'block-5.6-2020-03-07' of git://git.kernel.dk/linux-block

2020-03-07T20:14:38Z

Pull block fixes from Jens Axboe: "Here are a few fixes that should go into this release. This contains: - Revert of a bad bcache patch from this merge window - Removed unused function (Daniel) - Fixup for the blktrace fix from Jan from this release (Cengiz) - Fix of deeper level bfqq overwrite in BFQ (Carlo)" * tag 'block-5.6-2020-03-07' of git://git.kernel.dk/linux-block: block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group() blktrace: fix dereference after null check Revert "bcache: ignore pending signals when creating gc and allocator thread" block: Remove used kblockd_schedule_work_on()

bpf: Fix deadlock with rq_lock in bpf_send_signal()

2020-03-05T22:02:22Z

When experimenting with bpf_send_signal() helper in our production environment (5.2 based), we experienced a deadlock in NMI mode: #5 [ffffc9002219f770] queued_spin_lock_slowpath at ffffffff8110be24 #6 [ffffc9002219f770] _raw_spin_lock_irqsave at ffffffff81a43012 #7 [ffffc9002219f780] try_to_wake_up at ffffffff810e7ecd #8 [ffffc9002219f7e0] signal_wake_up_state at ffffffff810c7b55 #9 [ffffc9002219f7f0] __send_signal at ffffffff810c8602 #10 [ffffc9002219f830] do_send_sig_info at ffffffff810ca31a #11 [ffffc9002219f868] bpf_send_signal at ffffffff8119d227 #12 [ffffc9002219f988] bpf_overflow_handler at ffffffff811d4140 #13 [ffffc9002219f9e0] __perf_event_overflow at ffffffff811d68cf #14 [ffffc9002219fa10] perf_swevent_overflow at ffffffff811d6a09 #15 [ffffc9002219fa38] ___perf_sw_event at ffffffff811e0f47 #16 [ffffc9002219fc30] __schedule at ffffffff81a3e04d #17 [ffffc9002219fc90] schedule at ffffffff81a3e219 #18 [ffffc9002219fca0] futex_wait_queue_me at ffffffff8113d1b9 #19 [ffffc9002219fcd8] futex_wait at ffffffff8113e529 #20 [ffffc9002219fdf0] do_futex at ffffffff8113ffbc #21 [ffffc9002219fec0] __x64_sys_futex at ffffffff81140d1c #22 [ffffc9002219ff38] do_syscall_64 at ffffffff81002602 #23 [ffffc9002219ff50] entry_SYSCALL_64_after_hwframe at ffffffff81c00068 The above call stack is actually very similar to an issue reported by Commit eac9153f2b58 ("bpf/stackmap: Fix deadlock with rq_lock in bpf_get_stack()") by Song Liu. The only difference is bpf_send_signal() helper instead of bpf_get_stack() helper. The above deadlock is triggered with a perf_sw_event. Similar to Commit eac9153f2b58, the below almost identical reproducer used tracepoint point sched/sched_switch so the issue can be easily caught. /* stress_test.c */ #include #include #include #include #include #include #include #define THREAD_COUNT 1000 char *filename; void *worker(void *p) { void *ptr; int fd; char *pptr; fd = open(filename, O_RDONLY); if (fd < 0) return NULL; while (1) { struct timespec ts = {0, 1000 + rand() % 2000}; ptr = mmap(NULL, 4096 * 64, PROT_READ, MAP_PRIVATE, fd, 0); usleep(1); if (ptr == MAP_FAILED) { printf("failed to mmap\n"); break; } munmap(ptr, 4096 * 64); usleep(1); pptr = malloc(1); usleep(1); pptr[0] = 1; usleep(1); free(pptr); usleep(1); nanosleep(&ts, NULL); } close(fd); return NULL; } int main(int argc, char *argv[]) { void *ptr; int i; pthread_t threads[THREAD_COUNT]; if (argc < 2) return 0; filename = argv[1]; for (i = 0; i < THREAD_COUNT; i++) { if (pthread_create(threads + i, NULL, worker, NULL)) { fprintf(stderr, "Error creating thread\n"); return 0; } } for (i = 0; i < THREAD_COUNT; i++) pthread_join(threads[i], NULL); return 0; } and the following command: 1. run `stress_test /bin/ls` in one windown 2. hack bcc trace.py with the following change: --- a/tools/trace.py +++ b/tools/trace.py @@ -513,6 +513,7 @@ BPF_PERF_OUTPUT(%s); __data.tgid = __tgid; __data.pid = __pid; bpf_get_current_comm(&__data.comm, sizeof(__data.comm)); + bpf_send_signal(10); %s %s %s.perf_submit(%s, &__data, sizeof(__data)); 3. in a different window run ./trace.py -p $(pidof stress_test) t:sched:sched_switch The deadlock can be reproduced in our production system. Similar to Song's fix, the fix is to delay sending signal if irqs is disabled to avoid deadlocks involving with rq_lock. With this change, my above stress-test in our production system won't cause deadlock any more. I also implemented a scale-down version of reproducer in the selftest (a subsequent commit). With latest bpf-next, it complains for the following potential deadlock. [ 32.832450] -> #1 (&p->pi_lock){-.-.}: [ 32.833100] _raw_spin_lock_irqsave+0x44/0x80 [ 32.833696] task_rq_lock+0x2c/0xa0 [ 32.834182] task_sched_runtime+0x59/0xd0 [ 32.834721] thread_group_cputime+0x250/0x270 [ 32.835304] thread_group_cputime_adjusted+0x2e/0x70 [ 32.835959] do_task_stat+0x8a7/0xb80 [ 32.836461] proc_single_show+0x51/0xb0 ... [ 32.839512] -> #0 (&(&sighand->siglock)->rlock){....}: [ 32.840275] __lock_acquire+0x1358/0x1a20 [ 32.840826] lock_acquire+0xc7/0x1d0 [ 32.841309] _raw_spin_lock_irqsave+0x44/0x80 [ 32.841916] __lock_task_sighand+0x79/0x160 [ 32.842465] do_send_sig_info+0x35/0x90 [ 32.842977] bpf_send_signal+0xa/0x10 [ 32.843464] bpf_prog_bc13ed9e4d3163e3_send_signal_tp_sched+0x465/0x1000 [ 32.844301] trace_call_bpf+0x115/0x270 [ 32.844809] perf_trace_run_bpf_submit+0x4a/0xc0 [ 32.845411] perf_trace_sched_switch+0x10f/0x180 [ 32.846014] __schedule+0x45d/0x880 [ 32.846483] schedule+0x5f/0xd0 ... [ 32.853148] Chain exists of: [ 32.853148] &(&sighand->siglock)->rlock --> &p->pi_lock --> &rq->lock [ 32.853148] [ 32.854451] Possible unsafe locking scenario: [ 32.854451] [ 32.855173] CPU0 CPU1 [ 32.855745] ---- ---- [ 32.856278] lock(&rq->lock); [ 32.856671] lock(&p->pi_lock); [ 32.857332] lock(&rq->lock); [ 32.857999] lock(&(&sighand->siglock)->rlock); Deadlock happens on CPU0 when it tries to acquire &sighand->siglock but it has been held by CPU1 and CPU1 tries to grab &rq->lock and cannot get it. This is not exactly the callstack in our production environment, but sympotom is similar and both locks are using spin_lock_irqsave() to acquire the lock, and both involves rq_lock. The fix to delay sending signal when irq is disabled also fixed this issue. Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Cc: Song Liu Link: https://lore.kernel.org/bpf/20200304191104.2796501-1-yhs@fb.com

blktrace: fix dereference after null check

2020-03-05T20:42:40Z

There was a recent change in blktrace.c that added a RCU protection to `q->blk_trace` in order to fix a use-after-free issue during access. However the change missed an edge case that can lead to dereferencing of `bt` pointer even when it's NULL: Coverity static analyzer marked this as a FORWARD_NULL issue with CID 1460458. ``` /kernel/trace/blktrace.c: 1904 in sysfs_blk_trace_attr_store() 1898 ret = 0; 1899 if (bt == NULL) 1900 ret = blk_trace_setup_queue(q, bdev); 1901 1902 if (ret == 0) { 1903 if (attr == &dev_attr_act_mask) >>> CID 1460458: Null pointer dereferences (FORWARD_NULL) >>> Dereferencing null pointer "bt". 1904 bt->act_mask = value; 1905 else if (attr == &dev_attr_pid) 1906 bt->pid = value; 1907 else if (attr == &dev_attr_start_lba) 1908 bt->start_lba = value; 1909 else if (attr == &dev_attr_end_lba) ``` Added a reassignment with RCU annotation to fix the issue. Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU") Cc: stable@vger.kernel.org Reviewed-by: Ming Lei Reviewed-by: Bob Liu Reviewed-by: Steven Rostedt (VMware) Signed-off-by: Cengiz Can Signed-off-by: Jens Axboe

Merge tag 'block-5.6-2020-02-28' of git://git.kernel.dk/linux-block

2020-02-28T19:43:30Z

Pull block fixes from Jens Axboe: - Passthrough insertion fix (Ming) - Kill off some unused arguments (John) - blktrace RCU fix (Jan) - Dead fields removal for null_blk (Dongli) - NVMe polled IO fix (Bijan) * tag 'block-5.6-2020-02-28' of git://git.kernel.dk/linux-block: nvme-pci: Hold cq_poll_lock while completing CQEs blk-mq: Remove some unused function arguments null_blk: remove unused fields in 'nullb_cmd' blktrace: Protect q->blk_trace with RCU blk-mq: insert passthrough request into hctx->dispatch directly

Merge tag 'trace-v5.6-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2020-02-26T18:34:42Z

Pull tracing and bootconfig updates: "Fixes and changes to bootconfig before it goes live in a release. Change in API of bootconfig (before it comes live in a release): - Have a magic value "BOOTCONFIG" in initrd to know a bootconfig exists - Set CONFIG_BOOT_CONFIG to 'n' by default - Show error if "bootconfig" on cmdline but not compiled in - Prevent redefining the same value - Have a way to append values - Added a SELECT BLK_DEV_INITRD to fix a build failure Synthetic event fixes: - Switch to raw_smp_processor_id() for recording CPU value in preempt section. (No care for what the value actually is) - Fix samples always recording u64 values - Fix endianess - Check number of values matches number of fields - Fix a printing bug Fix of trace_printk() breaking postponed start up tests Make a function static that is only used in a single file" * tag 'trace-v5.6-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: bootconfig: Fix CONFIG_BOOTTIME_TRACING dependency issue bootconfig: Add append value operator support bootconfig: Prohibit re-defining value on same key bootconfig: Print array as multiple commands for legacy command line bootconfig: Reject subkey and value on same parent key tools/bootconfig: Remove unneeded error message silencer bootconfig: Add bootconfig magic word for indicating bootconfig explicitly bootconfig: Set CONFIG_BOOT_CONFIG=n by default tracing: Clear trace_state when starting trace bootconfig: Mark boot_config_checksum() static tracing: Disable trace_printk() on post poned tests tracing: Have synthetic event test use raw_smp_processor_id() tracing: Fix number printing bug in print_synth_event() tracing: Check that number of vals matches number of synth event fields tracing: Make synth_event trace functions endian-correct tracing: Make sure synth_event_trace() example always uses u64

bootconfig: Fix CONFIG_BOOTTIME_TRACING dependency issue

2020-02-26T00:07:58Z

Since commit d8a953ddde5e ("bootconfig: Set CONFIG_BOOT_CONFIG=n by default") also changed the CONFIG_BOOTTIME_TRACING to select CONFIG_BOOT_CONFIG to show the boot-time tracing on the menu, it introduced wrong dependencies with BLK_DEV_INITRD as below. WARNING: unmet direct dependencies detected for BOOT_CONFIG Depends on [n]: BLK_DEV_INITRD [=n] Selected by [y]: - BOOTTIME_TRACING [=y] && TRACING_SUPPORT [=y] && FTRACE [=y] && TRACING [=y] This makes the CONFIG_BOOT_CONFIG selects CONFIG_BLK_DEV_INITRD to fix this error and make CONFIG_BOOTTIME_TRACING=n by default, so that both boot-time tracing and boot configuration off but those appear on the menu list. Link: http://lkml.kernel.org/r/158264140162.23842.11237423518607465535.stgit@devnote2 Fixes: d8a953ddde5e ("bootconfig: Set CONFIG_BOOT_CONFIG=n by default") Reported-by: Randy Dunlap Compiled-tested-by: Randy Dunlap Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware)

blktrace: Protect q->blk_trace with RCU

2020-02-25T15:40:07Z

KASAN is reporting that __blk_add_trace() has a use-after-free issue when accessing q->blk_trace. Indeed the switching of block tracing (and thus eventual freeing of q->blk_trace) is completely unsynchronized with the currently running tracing and thus it can happen that the blk_trace structure is being freed just while __blk_add_trace() works on it. Protect accesses to q->blk_trace by RCU during tracing and make sure we wait for the end of RCU grace period when shutting down tracing. Luckily that is rare enough event that we can afford that. Note that postponing the freeing of blk_trace to an RCU callback should better be avoided as it could have unexpected user visible side-effects as debugfs files would be still existing for a short while block tracing has been shut down. Link: https://bugzilla.kernel.org/show_bug.cgi?id=205711 CC: stable@vger.kernel.org Reviewed-by: Chaitanya Kulkarni Reviewed-by: Ming Lei Tested-by: Ming Lei Reviewed-by: Bart Van Assche Reported-by: Tristan Madani Signed-off-by: Jan Kara Signed-off-by: Jens Axboe