From: Pu Lehui <[email protected]>
When the length of the string written to set_ftrace_filter exceeds
FTRACE_BUFF_MAX, the following KASAN alarm will be triggered:
BUG: KASAN: slab-out-of-bounds in strsep+0x18c/0x1b0
Read of size 1 at addr ffff0000d00bd5ba by task ash/165
CPU: 1 UID: 0 PID: 165 Comm: ash Not tainted 6.16.0-g6bcdbd62bd56-dirty
Hardware name: linux,dummy-virt (DT)
Call trace:
show_stack+0x34/0x50 (C)
dump_stack_lvl+0xa0/0x158
print_address_description.constprop.0+0x88/0x398
print_report+0xb0/0x280
kasan_report+0xa4/0xf0
__asan_report_load1_noabort+0x20/0x30
strsep+0x18c/0x1b0
ftrace_process_regex.isra.0+0x100/0x2d8
ftrace_regex_release+0x484/0x618
__fput+0x364/0xa58
____fput+0x28/0x40
task_work_run+0x154/0x278
do_notify_resume+0x1f0/0x220
el0_svc+0xec/0xf0
el0t_64_sync_handler+0xa0/0xe8
el0t_64_sync+0x1ac/0x1b0
The reason is that trace_get_user will fail when processing a string
longer than FTRACE_BUFF_MAX, but not set the end of parser->buffer to 0.
Then an OOB access will be triggered in ftrace_regex_release->
ftrace_process_regex->strsep->strpbrk. We can solve this problem by
limiting access to parser->buffer when trace_get_user failed.
Fixes: 8c9af478c06b ("ftrace: Handle commands when closing set_ftrace_filter
file")
Signed-off-by: Pu Lehui <[email protected]>
---
v2:
- Add `fail` field to struct trace_parser to indicate parsing failed.
v1:
https://lore.kernel.org/all/[email protected]/
kernel/trace/trace.c | 20 ++++++++++++++------
kernel/trace/trace.h | 3 ++-
2 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4283ed4e8f59..138212f4ecde 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1814,9 +1814,11 @@ int trace_get_user(struct trace_parser *parser, const
char __user *ubuf,
if (!*ppos)
trace_parser_clear(parser);
+ parser->fail = false;
+
ret = get_user(ch, ubuf++);
if (ret)
- return ret;
+ goto fail;
read++;
cnt--;
@@ -1830,7 +1832,7 @@ int trace_get_user(struct trace_parser *parser, const
char __user *ubuf,
while (cnt && isspace(ch)) {
ret = get_user(ch, ubuf++);
if (ret)
- return ret;
+ goto fail;
read++;
cnt--;
}
@@ -1848,12 +1850,14 @@ int trace_get_user(struct trace_parser *parser, const
char __user *ubuf,
while (cnt && !isspace(ch) && ch) {
if (parser->idx < parser->size - 1)
parser->buffer[parser->idx++] = ch;
- else
- return -EINVAL;
+ else {
+ ret = -EINVAL;
+ goto fail;
+ }
ret = get_user(ch, ubuf++);
if (ret)
- return ret;
+ goto fail;
read++;
cnt--;
}
@@ -1868,11 +1872,15 @@ int trace_get_user(struct trace_parser *parser, const
char __user *ubuf,
/* Make sure the parsed string always terminates with '\0'. */
parser->buffer[parser->idx] = 0;
} else {
- return -EINVAL;
+ ret = -EINVAL;
+ goto fail;
}
*ppos += read;
return read;
+fail:
+ parser->fail = true;
+ return ret;
}
/* TODO add a seq_buf_to_buffer() */
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 1dbf1d3cf2f1..5072bb25a860 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1292,6 +1292,7 @@ bool ftrace_event_is_function(struct trace_event_call
*call);
*/
struct trace_parser {
bool cont;
+ bool fail;
char *buffer;
unsigned idx;
unsigned size;
@@ -1299,7 +1300,7 @@ struct trace_parser {
static inline bool trace_parser_loaded(struct trace_parser *parser)
{
- return (parser->idx != 0);
+ return !parser->fail && parser->idx != 0;
}
static inline bool trace_parser_cont(struct trace_parser *parser)
--
2.34.1
