From cda1fbfc5313bb90daa271d45eea4a8d317a8544 Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Thu, 25 Jun 2026 08:34:46 +0900 Subject: tracing/events: Fix to check the simple_tsk_fn creation Sashiko pointed that this sample code does not correctly handle the failure of thread creation because kthread_run() can return -errno. Check the simple_tsk_fn is correctly initialized (created) or not. Link: https://lore.kernel.org/all/178165817322.269421.3992299509400184196.stgit@devnote2/ Link: https://sashiko.dev/#/patchset/178092865666.163648.10457567771536160909.stgit%40devnote2 Fixes: 9cfe06f8cd5c ("tracing/events: add trace-events-sample") Signed-off-by: Masami Hiramatsu (Google) --- samples/trace_events/trace-events-sample.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'samples') diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c index ecc7db237f2e..0b7a6efdb247 100644 --- a/samples/trace_events/trace-events-sample.c +++ b/samples/trace_events/trace-events-sample.c @@ -107,6 +107,10 @@ int foo_bar_reg(void) * for consistency sake, we still take the thread_mutex. */ simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn"); + if (IS_ERR_OR_NULL(simple_tsk_fn)) { + pr_err("Failed to create simple_thread_fn\n"); + simple_tsk_fn = NULL; + } out: mutex_unlock(&thread_mutex); return 0; -- cgit From 7746d72c64054976887928d64d2caf25c5a6dcc0 Mon Sep 17 00:00:00 2001 From: Zenghui Yu Date: Mon, 29 Jun 2026 07:44:31 -0700 Subject: samples/damon/mtier: fail early if address range parameters are invalid The comment on top of `struct damon_region` clearly says that For any use case, @ar should be non-zero positive size. which is now verified in damon_verify_new_region() if the kernel is built with DAMON_DEBUG_SANITY. The WARN_ONCE() can be triggered if the mtier sample module is enabled before node{0,1}_{start,end}_addr have been properly initialized, which is obviously not good. ------------[ cut here ]------------ start 0 >= end 0 WARNING: mm/damon/core.c:217 at damon_new_region+0xf4/0x118, CPU#59: bash/341468 Call trace: damon_new_region+0xf4/0x118 (P) damon_set_regions+0xfc/0x3c0 damon_sample_mtier_build_ctx+0xe8/0x3a8 damon_sample_mtier_start+0x1c/0x90 damon_sample_mtier_enable_store+0x98/0xb0 param_attr_store+0xb4/0x128 module_attr_store+0x2c/0x50 sysfs_kf_write+0x58/0x90 kernfs_fop_write_iter+0x16c/0x238 vfs_write+0x2c0/0x370 ksys_write+0x74/0x118 __arm64_sys_write+0x24/0x38 invoke_syscall+0xa8/0x118 el0_svc_common.constprop.0+0x48/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x54/0x370 el0t_64_sync_handler+0xa0/0xe8 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Note that the same issue can happen if detect_node_addresses is true, and node 0 or 1 is memoryless. Fix it together by checking the validity of parameters right before damon_new_region() and fail early if they're invalid. Link: https://lore.kernel.org/20260629144432.133962-1-sj@kernel.org Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Signed-off-by: Zenghui Yu Signed-off-by: SJ Park Reviewed-by: SJ Park Cc: # 6.16.x Signed-off-by: Andrew Morton --- samples/damon/mtier.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'samples') diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c index eb1143de8df1..3785b0c7ffb1 100644 --- a/samples/damon/mtier.c +++ b/samples/damon/mtier.c @@ -120,6 +120,9 @@ static struct damon_ctx *damon_sample_mtier_build_ctx(bool promote) addr.end = promote ? node1_end_addr : node0_end_addr; } + if (addr.start >= addr.end) + goto free_out; + range.start = addr.start; range.end = addr.end; -- cgit From e5d8524108fef14970db85451b7d06e5f6fa51ce Mon Sep 17 00:00:00 2001 From: Yudistira Putra Date: Sun, 21 Jun 2026 05:51:53 -0400 Subject: samples: ftrace: Fix typos in benchmark comment Fix two typos in the ftrace operations sample benchmark comment. Link: https://patch.msgid.link/20260621095153.93762-1-pyudistira519@gmail.com Signed-off-by: Yudistira Putra Signed-off-by: Steven Rostedt --- samples/ftrace/ftrace-ops.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'samples') diff --git a/samples/ftrace/ftrace-ops.c b/samples/ftrace/ftrace-ops.c index 68d6685c80bd..152ffc1a30b6 100644 --- a/samples/ftrace/ftrace-ops.c +++ b/samples/ftrace/ftrace-ops.c @@ -232,8 +232,8 @@ static int __init ftrace_ops_sample_init(void) ops_destroy(ops_irrelevant, nr_ops_irrelevant); /* - * The benchmark completed sucessfully, but there's no reason to keep - * the module around. Return an error do the user doesn't have to + * The benchmark completed successfully, but there's no reason to keep + * the module around. Return an error so the user doesn't have to * manually unload the module. */ return -EINVAL; -- cgit From a16fd3ad9d89b05475864da97327870464611736 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Mon, 3 Aug 2026 06:40:32 -0700 Subject: samples/damon/mtier: error out for zero quota goal target values Patch series "mm/damon: avoid division by zero from damos_quota_score()". DAMON_SAMPLE_MTIER and DAMON_LRU_SORT allow the user to trigger division by zero in damos_quota_score(). Avoid it by adding parameters validation checks. This patch (of 2): damos_quota_score() can trigger division by zero if the target_value is zero. DAMON_SAMPLE_MTIER lets users set the target_value via node0_mem_{used,free}_bp parameters. It doesn't guard zero value case, though. As a result, users can trigger division by zero. Fix the issue by returning an error when the user tries to start DAMON with zero node0_mem_{used,free}_bp parameter values. DAMON_SAMPLE_MTIER is just a sample module, but the consequence is quite bad. Also the zero node0_mem_free_bp parameter might look like a reasonable setup to some users. Hence, the issue might really happen in the real world. One reliable way to reproduce the issue is like below: # cd /sys/module/damon_sample_mtier/parameters # echo 4096 > node0_start_addr # echo 8192 > node0_end_addr # echo 8192 > node1_start_addr # echo 81920 > node1_end_addr # echo 0 > node0_mem_free_bp # echo Y > enabled # dmesg -w [...] [18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI [...] [18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480 [...] This issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260803134034.15217-1-sj@kernel.org Link: https://lore.kernel.org/20260803134034.15217-2-sj@kernel.org Link: https://lore.kernel.org/20260801202657.117135-1-sj@kernel.org [1] Fixes: c5e67d40a102 ("samples/damon/mtier: add parameters for node0 memory usage") Signed-off-by: SJ Park Cc: # 6.17.x Signed-off-by: Andrew Morton --- samples/damon/mtier.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'samples') diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c index 3785b0c7ffb1..dae6929f827c 100644 --- a/samples/damon/mtier.c +++ b/samples/damon/mtier.c @@ -156,6 +156,9 @@ static struct damon_ctx *damon_sample_mtier_build_ctx(bool promote) if (!scheme) goto free_out; damon_set_schemes(ctx, &scheme, 1); + /* zero target value causes division by zero in damos_quota_store() */ + if (!node0_mem_used_bp || !node0_mem_free_bp) + goto free_out; quota_goal = damos_new_quota_goal( promote ? DAMOS_QUOTA_NODE_MEM_USED_BP : DAMOS_QUOTA_NODE_MEM_FREE_BP, -- cgit