[ Upstream commit 761a8c58db6bc884994b28cd6d9707b467d680c1 ]
There was a memory corruption bug happening while running the synthetic event selftests:
kmemleak: Cannot insert 0xffff8c196fa2afe5 into the object search tree (overlaps existing) CPU: 5 PID: 6866 Comm: ftracetest Tainted: G W 5.9.0-rc5-test+ #577 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 Call Trace: dump_stack+0x8d/0xc0 create_object.cold+0x3b/0x60 slab_post_alloc_hook+0x57/0x510 ? tracing_map_init+0x178/0x340 __kmalloc+0x1b1/0x390 tracing_map_init+0x178/0x340 event_hist_trigger_func+0x523/0xa40 trigger_process_regex+0xc5/0x110 event_trigger_write+0x71/0xd0 vfs_write+0xca/0x210 ksys_write+0x70/0xf0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fef0a63a487 Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 RSP: 002b:00007fff76f18398 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000039 RCX: 00007fef0a63a487 RDX: 0000000000000039 RSI: 000055eb3b26d690 RDI: 0000000000000001 RBP: 000055eb3b26d690 R08: 000000000000000a R09: 0000000000000038 R10: 000055eb3b2cdb80 R11: 0000000000000246 R12: 0000000000000039 R13: 00007fef0a70b500 R14: 0000000000000039 R15: 00007fef0a70b700 kmemleak: Kernel memory leak detector disabled kmemleak: Object 0xffff8c196fa2afe0 (size 8): kmemleak: comm "ftracetest", pid 6866, jiffies 4295082531 kmemleak: min_count = 1 kmemleak: count = 0 kmemleak: flags = 0x1 kmemleak: checksum = 0 kmemleak: backtrace: __kmalloc+0x1b1/0x390 tracing_map_init+0x1be/0x340 event_hist_trigger_func+0x523/0xa40 trigger_process_regex+0xc5/0x110 event_trigger_write+0x71/0xd0 vfs_write+0xca/0x210 ksys_write+0x70/0xf0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9
The cause came down to a use of strcat() that was adding an string that was shorten, but the strcat() did not take that into account.
strcat() is extremely dangerous as it does not care how big the buffer is. Replace it with seq_buf operations that prevent the buffer from being overwritten if what is being written is bigger than the buffer.
Fixes: 10819e25799a ("tracing: Handle synthetic event array field type checking correctly") Reviewed-by: Tom Zanussi zanussi@kernel.org Tested-by: Tom Zanussi zanussi@kernel.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace_events_synth.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index c8892156db341..65e8c27141c02 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -465,6 +465,7 @@ static struct synth_field *parse_synth_field(int argc, const char **argv, struct synth_field *field; const char *prefix = NULL, *field_type = argv[0], *field_name, *array; int len, ret = 0; + struct seq_buf s; ssize_t size;
if (field_type[0] == ';') @@ -503,13 +504,9 @@ static struct synth_field *parse_synth_field(int argc, const char **argv, field_type++; len = strlen(field_type) + 1;
- if (array) { - int l = strlen(array); + if (array) + len += strlen(array);
- if (l && array[l - 1] == ';') - l--; - len += l; - } if (prefix) len += strlen(prefix);
@@ -518,14 +515,18 @@ static struct synth_field *parse_synth_field(int argc, const char **argv, ret = -ENOMEM; goto free; } + seq_buf_init(&s, field->type, len); if (prefix) - strcat(field->type, prefix); - strcat(field->type, field_type); + seq_buf_puts(&s, prefix); + seq_buf_puts(&s, field_type); if (array) { - strcat(field->type, array); - if (field->type[len - 1] == ';') - field->type[len - 1] = '\0'; + seq_buf_puts(&s, array); + if (s.buffer[s.len - 1] == ';') + s.len--; } + if (WARN_ON_ONCE(!seq_buf_buffer_left(&s))) + goto free; + s.buffer[s.len] = '\0';
size = synth_field_size(field->type); if (size <= 0) {