From f86b0aaad741c45aba5a84a27277dd56a96808ba Mon Sep 17 00:00:00 2001 From: Kalesh Singh Date: Wed, 17 Nov 2021 17:15:42 -0800 Subject: tracing/histogram: Fix UAF in destroy_hist_field() Calling destroy_hist_field() on an expression will recursively free any operands associated with the expression. If during expression parsing the operands of the expression are already set when an error is encountered, there is no need to explicity free the operands. Doing so will result in destroy_hist_field() being called twice for the operands and lead to a use-after-free (UAF) error. If the operands are associated with the expression, only call destroy_hist_field() on the expression since the operands will be recursively freed. Link: https://lore.kernel.org/all/CAHk-=wgcrEbFgkw9720H3tW-AhHOoEKhYwZinYJw4FpzSaJ6_Q@mail.gmail.com/ Link: https://lkml.kernel.org/r/20211118011542.1420131-1-kaleshsingh@google.com Suggested-by: Linus Torvalds Signed-off-by: Kalesh Singh Fixes: 8b5d46fd7a38 ("tracing/histogram: Optimize division by constants") Reported-by: kernel test robot Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_hist.c | 41 +++++++++++++++++++++------------------- 1 file changed, 22 insertions(+), 19 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 5ea2c9ec54a6..9555b8e1d1e3 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -2576,28 +2576,27 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, /* Split the expression string at the root operator */ if (!sep) - goto free; + return ERR_PTR(-EINVAL); + *sep = '\0'; operand1_str = str; str = sep+1; /* Binary operator requires both operands */ if (*operand1_str == '\0' || *str == '\0') - goto free; + return ERR_PTR(-EINVAL); operand_flags = 0; /* LHS of string is an expression e.g. a+b in a+b+c */ operand1 = parse_expr(hist_data, file, operand1_str, operand_flags, NULL, n_subexprs); - if (IS_ERR(operand1)) { - ret = PTR_ERR(operand1); - operand1 = NULL; - goto free; - } + if (IS_ERR(operand1)) + return ERR_CAST(operand1); + if (operand1->flags & HIST_FIELD_FL_STRING) { hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(operand1_str)); ret = -EINVAL; - goto free; + goto free_op1; } /* RHS of string is another expression e.g. c in a+b+c */ @@ -2605,13 +2604,12 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, n_subexprs); if (IS_ERR(operand2)) { ret = PTR_ERR(operand2); - operand2 = NULL; - goto free; + goto free_op1; } if (operand2->flags & HIST_FIELD_FL_STRING) { hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(str)); ret = -EINVAL; - goto free; + goto free_operands; } switch (field_op) { @@ -2629,12 +2627,12 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, break; default: ret = -EINVAL; - goto free; + goto free_operands; } ret = check_expr_operands(file->tr, operand1, operand2, &var1, &var2); if (ret) - goto free; + goto free_operands; operand_flags = var1 ? var1->flags : operand1->flags; operand2_flags = var2 ? var2->flags : operand2->flags; @@ -2653,12 +2651,13 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, expr = create_hist_field(hist_data, NULL, flags, var_name); if (!expr) { ret = -ENOMEM; - goto free; + goto free_operands; } operand1->read_once = true; operand2->read_once = true; + /* The operands are now owned and free'd by 'expr' */ expr->operands[0] = operand1; expr->operands[1] = operand2; @@ -2669,7 +2668,7 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, if (!divisor) { hist_err(file->tr, HIST_ERR_DIVISION_BY_ZERO, errpos(str)); ret = -EDOM; - goto free; + goto free_expr; } /* @@ -2709,18 +2708,22 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, expr->type = kstrdup_const(operand1->type, GFP_KERNEL); if (!expr->type) { ret = -ENOMEM; - goto free; + goto free_expr; } expr->name = expr_str(expr, 0); } return expr; -free: - destroy_hist_field(operand1, 0); + +free_operands: destroy_hist_field(operand2, 0); - destroy_hist_field(expr, 0); +free_op1: + destroy_hist_field(operand1, 0); + return ERR_PTR(ret); +free_expr: + destroy_hist_field(expr, 0); return ERR_PTR(ret); } -- cgit v1.2.3 From c4c1dbcc09e723295969a62aff401815b7ee15f4 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 18 Nov 2021 12:22:17 -0800 Subject: tracing: Use memset_startat() to zero struct trace_iterator In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memset(), avoid intentionally writing across neighboring fields. Use memset_startat() to avoid confusing memset() about writing beyond the target struct member. Link: https://lkml.kernel.org/r/20211118202217.1285588-1-keescook@chromium.org Signed-off-by: Kees Cook Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f9139dc1262c..e3c80cfd4eec 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6706,9 +6706,7 @@ waitagain: cnt = PAGE_SIZE - 1; /* reset all but tr, trace, and overruns */ - memset(&iter->seq, 0, - sizeof(struct trace_iterator) - - offsetof(struct trace_iterator, seq)); + memset_startat(iter, 0, seq); cpumask_clear(iter->started); trace_seq_init(&iter->seq); iter->pos = -1; -- cgit v1.2.3 From 2ef75e9bd2c998f1c6f6f23a3744136105ddefd5 Mon Sep 17 00:00:00 2001 From: Nikita Yushchenko Date: Thu, 18 Nov 2021 17:55:16 +0300 Subject: tracing: Don't use out-of-sync va_list in event printing If trace_seq becomes full, trace_seq_vprintf() no longer consumes arguments from va_list, making va_list out of sync with format processing by trace_check_vprintf(). This causes va_arg() in trace_check_vprintf() to return wrong positional argument, which results into a WARN_ON_ONCE() hit. ftrace_stress_test from LTP triggers this situation. Fix it by explicitly avoiding further use if va_list at the point when it's consistency can no longer be guaranteed. Link: https://lkml.kernel.org/r/20211118145516.13219-1-nikita.yushchenko@virtuozzo.com Signed-off-by: Nikita Yushchenko Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'kernel') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index e3c80cfd4eec..88de94da596b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3812,6 +3812,18 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, iter->fmt[i] = '\0'; trace_seq_vprintf(&iter->seq, iter->fmt, ap); + /* + * If iter->seq is full, the above call no longer guarantees + * that ap is in sync with fmt processing, and further calls + * to va_arg() can return wrong positional arguments. + * + * Ensure that ap is no longer used in this case. + */ + if (iter->seq.full) { + p = ""; + break; + } + if (star) len = va_arg(ap, int); -- cgit v1.2.3