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Message-Id: <20231214000620.3081018-1-lucas.demarchi@intel.com> Date: Wed, 13 Dec 2023 16:06:20 -0800 From: Lucas De Marchi <lucas.demarchi@...el.com> To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org> Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, Lucas De Marchi <lucas.demarchi@...el.com> Subject: [PATCH] Revert "perf: Fix perf_event_validate_size()" This reverts commit 382c27f4ed28f803b1f1473ac2d8db0afc795a1b. When using for_each_sibling_event() lockdep complains on WARN_ON_ONCE(__lockdep_enabled && \ (this_cpu_read(hardirqs_enabled) && \ lockdep_is_held(&(event)->ctx->mutex) != LOCK_STATE_HELD)) after a simple `perf stat -e instructions sleep 1`: WARNING: CPU: 8 PID: 1471 at kernel/events/core.c:1950 __do_sys_perf_event_open+0xf37/0x1080 Modules linked in: x86_pkg_temp_thermal coretemp kvm_intel kvm e1000e igc irqbypass mei_pxp mei_hdcp crct10dif_pclmul wmi_bmof crc32_pclmul ghash_clmulni_intel i2c_i801 ptp mei_me i2c_smbus pps_core mei intel_lpss_pci video wmi fuse CPU: 8 PID: 1471 Comm: perf Not tainted 6.7.0-rc5-linus-demarchi+ #8 Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 4L ERB, BIOS RKLSFWI1.R00.2022.A00.2101052151 01/05/2021 RIP: 0010:__do_sys_perf_event_open+0xf37/0x1080 Code: ff e8 ed 30 ab 00 48 8b 81 28 02 00 00 83 ce ff 48 8d b8 a8 00 00 00 e8 67 38 ab 00 48 8b 4c 24 08 83 e8 01 0f 84 56 f9 ff ff <0f> 0b e9 4f f9 ff ff be 03 00 00 00 e8 d8 74 40 00 e9 54 fa ff ff RSP: 0018:ffffc90001d6be40 EFLAGS: 00010297 RAX: 00000000ffffffff RBX: ffff888112bc8040 RCX: ffff888100c34568 RDX: 0000000080000000 RSI: ffffffff823e2806 RDI: ffffffff824023cb RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000001 R11: 0000000000000000 R12: ffff888106560800 R13: 0000000000000000 R14: 0000000000080002 R15: ffff888100c34568 FS: 00007f723d196c00(0000) GS:ffff888450800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005624c0efdaa0 CR3: 00000001199de002 CR4: 0000000000770ef0 PKRU: 55555554 Call Trace: <TASK> ? __do_sys_perf_event_open+0xf37/0x1080 ? __warn+0x80/0x170 ? __do_sys_perf_event_open+0xf37/0x1080 ? report_bug+0x191/0x1c0 ? handle_bug+0x3c/0x70 ? exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? __do_sys_perf_event_open+0xf37/0x1080 do_syscall_64+0x42/0xf0 entry_SYSCALL_64_after_hwframe+0x6e/0x76 RIP: 0033:0x7f723bf1ea7d Code: 5b 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 83 a3 0f 00 f7 d8 64 89 01 48 RSP: 002b:00007ffc7118ba68 EFLAGS: 00000246 ORIG_RAX: 000000000000012a RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007f723bf1ea7d RDX: 00000000ffffffff RSI: 00000000000005c0 RDI: 00005624c0efb0c0 RBP: 00007ffc7118bb20 R08: 0000000000000008 R09: 0000000000000000 R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000008 R14: 00005624c0efb0b0 R15: 00005624c0efb0b0 </TASK> irq event stamp: 45697 hardirqs last enabled at (45703): [<ffffffff81173dca>] console_unlock+0x10a/0x160 hardirqs last disabled at (45708): [<ffffffff81173daf>] console_unlock+0xef/0x160 softirqs last enabled at (45276): [<ffffffff810dab0e>] irq_exit_rcu+0x8e/0xf0 softirqs last disabled at (45267): [<ffffffff810dab0e>] irq_exit_rcu+0x8e/0xf0 References: https://gitlab.freedesktop.org/drm/intel/-/issues/9847 Signed-off-by: Lucas De Marchi <lucas.demarchi@...el.com> --- Not sure about a proper fix for this. At first I thought it was indeed because previously it was not validating the the size correctly. However then I noticed the warning is actually due to for_each_sibling_event(). kernel/events/core.c | 61 +++++++++++++++++--------------------------- 1 file changed, 23 insertions(+), 38 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index c9d123e13b57..b704d83a28b2 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1814,34 +1814,31 @@ static inline void perf_event__state_init(struct perf_event *event) PERF_EVENT_STATE_INACTIVE; } -static int __perf_event_read_size(u64 read_format, int nr_siblings) +static void __perf_event_read_size(struct perf_event *event, int nr_siblings) { int entry = sizeof(u64); /* value */ int size = 0; int nr = 1; - if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) + if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) size += sizeof(u64); - if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) + if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) size += sizeof(u64); - if (read_format & PERF_FORMAT_ID) + if (event->attr.read_format & PERF_FORMAT_ID) entry += sizeof(u64); - if (read_format & PERF_FORMAT_LOST) + if (event->attr.read_format & PERF_FORMAT_LOST) entry += sizeof(u64); - if (read_format & PERF_FORMAT_GROUP) { + if (event->attr.read_format & PERF_FORMAT_GROUP) { nr += nr_siblings; size += sizeof(u64); } - /* - * Since perf_event_validate_size() limits this to 16k and inhibits - * adding more siblings, this will never overflow. - */ - return size + nr * entry; + size += entry * nr; + event->read_size = size; } static void __perf_event_header_size(struct perf_event *event, u64 sample_type) @@ -1891,9 +1888,8 @@ static void __perf_event_header_size(struct perf_event *event, u64 sample_type) */ static void perf_event__header_size(struct perf_event *event) { - event->read_size = - __perf_event_read_size(event->attr.read_format, - event->group_leader->nr_siblings); + __perf_event_read_size(event, + event->group_leader->nr_siblings); __perf_event_header_size(event, event->attr.sample_type); } @@ -1924,35 +1920,24 @@ static void perf_event__id_header_size(struct perf_event *event) event->id_header_size = size; } -/* - * Check that adding an event to the group does not result in anybody - * overflowing the 64k event limit imposed by the output buffer. - * - * Specifically, check that the read_size for the event does not exceed 16k, - * read_size being the one term that grows with groups size. Since read_size - * depends on per-event read_format, also (re)check the existing events. - * - * This leaves 48k for the constant size fields and things like callchains, - * branch stacks and register sets. - */ static bool perf_event_validate_size(struct perf_event *event) { - struct perf_event *sibling, *group_leader = event->group_leader; - - if (__perf_event_read_size(event->attr.read_format, - group_leader->nr_siblings + 1) > 16*1024) - return false; + /* + * The values computed here will be over-written when we actually + * attach the event. + */ + __perf_event_read_size(event, event->group_leader->nr_siblings + 1); + __perf_event_header_size(event, event->attr.sample_type & ~PERF_SAMPLE_READ); + perf_event__id_header_size(event); - if (__perf_event_read_size(group_leader->attr.read_format, - group_leader->nr_siblings + 1) > 16*1024) + /* + * Sum the lot; should not exceed the 64k limit we have on records. + * Conservative limit to allow for callchains and other variable fields. + */ + if (event->read_size + event->header_size + + event->id_header_size + sizeof(struct perf_event_header) >= 16*1024) return false; - for_each_sibling_event(sibling, group_leader) { - if (__perf_event_read_size(sibling->attr.read_format, - group_leader->nr_siblings + 1) > 16*1024) - return false; - } - return true; } -- 2.40.1
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