When creating a trace_probe we would set nr_args prior to truncating the arguments to MAX_TRACE_ARGS. However, we would only initialize arguments up to the limit.
This caused invalid memory access when attempting to set up probes with more than 128 fetchargs. BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 UID: 0 PID: 1769 Comm: cat Not tainted 6.11.0-rc7+ #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014 RIP: 0010:__set_print_fmt+0x134/0x330 Resolve the issue by applying the MAX_TRACE_ARGS limit earlier. This restores the prior behaviour of silently ignoring excess arguments. Fixes: 035ba76014c0 ("tracing/probes: cleanup: Set trace_probe::nr_args at trace_probe_init") Signed-off-by: Mikel Rychliski <mi...@mikelr.com> --- kernel/trace/trace_eprobe.c | 5 +++-- kernel/trace/trace_fprobe.c | 3 ++- kernel/trace/trace_kprobe.c | 3 ++- kernel/trace/trace_uprobe.c | 3 ++- 4 files changed, 9 insertions(+), 5 deletions(-) diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index b0e0ec85912e..62c1a1fba403 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -914,7 +914,7 @@ static int __trace_eprobe_create(int argc, const char *argv[]) mutex_lock(&event_mutex); event_call = find_and_get_event(sys_name, sys_event); - ep = alloc_event_probe(group, event, event_call, argc - 2); + ep = alloc_event_probe(group, event, event_call, min(argc - 2, MAX_TRACE_ARGS)); mutex_unlock(&event_mutex); if (IS_ERR(ep)) { @@ -936,8 +936,9 @@ static int __trace_eprobe_create(int argc, const char *argv[]) ep->filter_str = NULL; argc -= 2; argv += 2; + argc = min(argc, MAX_TRACE_ARGS); /* parse arguments */ - for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { + for (i = 0; i < argc; i++) { trace_probe_log_set_index(i + 2); ret = trace_eprobe_tp_update_arg(ep, argv, i); if (ret) diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c index a079abd8955b..ca72fe8a04e7 100644 --- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -1187,6 +1187,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) argc = new_argc; argv = new_argv; } + argc = min(argc, MAX_TRACE_ARGS); ret = traceprobe_expand_dentry_args(argc, argv, &dbuf); if (ret) @@ -1203,7 +1204,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) } /* parse arguments */ - for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { + for (i = 0; i < argc; i++) { trace_probe_log_set_index(i + 2); ctx.offset = 0; ret = traceprobe_parse_probe_arg(&tf->tp, i, argv[i], &ctx); diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 61a6da808203..10d16b574db5 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1013,6 +1013,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) argc = new_argc; argv = new_argv; } + argc = min(argc, MAX_TRACE_ARGS); ret = traceprobe_expand_dentry_args(argc, argv, &dbuf); if (ret) @@ -1029,7 +1030,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) } /* parse arguments */ - for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { + for (i = 0; i < argc; i++) { trace_probe_log_set_index(i + 2); ctx.offset = 0; ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], &ctx); diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index c3df411a2684..985d23d57702 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -676,6 +676,7 @@ static int __trace_uprobe_create(int argc, const char **argv) argc -= 2; argv += 2; + argc = min(argc, MAX_TRACE_ARGS); tu = alloc_trace_uprobe(group, event, argc, is_return); if (IS_ERR(tu)) { @@ -690,7 +691,7 @@ static int __trace_uprobe_create(int argc, const char **argv) tu->filename = filename; /* parse arguments */ - for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { + for (i = 0; i < argc; i++) { struct traceprobe_parse_context ctx = { .flags = (is_return ? TPARG_FL_RETURN : 0) | TPARG_FL_USER, }; base-commit: 886f3732878dc92fb0ad6d8b6740b66410d1d50a -- 2.46.1