d1776c0202
The filter string doesn't get freed when a dynamic event is deleted. If a
filter is set, then memory is leaked:
root@localhost:/sys/kernel/tracing# echo 'e:egroup/stat_runtime_4core \
sched/sched_stat_runtime runtime=$runtime:u32 if cpu < 4' >> dynamic_events
root@localhost:/sys/kernel/tracing# echo "-:egroup/stat_runtime_4core" >> dynamic_events
root@localhost:/sys/kernel/tracing# echo scan > /sys/kernel/debug/kmemleak
[ 224.416373] kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
root@localhost:/sys/kernel/tracing# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff88810156f1b8 (size 8):
comm "bash", pid 224, jiffies 4294935612 (age 55.800s)
hex dump (first 8 bytes):
63 70 75 20 3c 20 34 00 cpu < 4.
backtrace:
[<000000009f880725>] __kmem_cache_alloc_node+0x18e/0x720
[<0000000042492946>] __kmalloc+0x57/0x240
[<0000000034ea7995>] __trace_eprobe_create+0x1214/0x1d30
[<00000000d70ef730>] trace_probe_create+0xf6/0x110
[<00000000915c7b16>] eprobe_dyn_event_create+0x21/0x30
[<000000000d894386>] create_dyn_event+0xf3/0x1a0
[<00000000e9af57d5>] trace_parse_run_command+0x1a9/0x2e0
[<0000000080777f18>] dyn_event_write+0x39/0x50
[<0000000089f0ec73>] vfs_write+0x311/0xe50
[<000000003da1bdda>] ksys_write+0x158/0x2a0
[<00000000bb1e616e>] __x64_sys_write+0x7c/0xc0
[<00000000e8aef1f7>] do_syscall_64+0x60/0x90
[<00000000fe7fe8ba>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
Additionally, in __trace_eprobe_create() function, if an error occurs after
the call to trace_eprobe_parse_filter(), which allocates the filter string,
then memory is also leaked. That can be reproduced by creating the same
event probe twice:
root@localhost:/sys/kernel/tracing# echo 'e:egroup/stat_runtime_4core \
sched/sched_stat_runtime runtime=$runtime:u32 if cpu < 4' >> dynamic_events
root@localhost:/sys/kernel/tracing# echo 'e:egroup/stat_runtime_4core \
sched/sched_stat_runtime runtime=$runtime:u32 if cpu < 4' >> dynamic_events
-bash: echo: write error: File exists
root@localhost:/sys/kernel/tracing# echo scan > /sys/kernel/debug/kmemleak
[ 207.871584] kmemleak: 1 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
root@localhost:/sys/kernel/tracing# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff8881020d17a8 (size 8):
comm "bash", pid 223, jiffies 4294938308 (age 31.000s)
hex dump (first 8 bytes):
63 70 75 20 3c 20 34 00 cpu < 4.
backtrace:
[<000000000e4f5f31>] __kmem_cache_alloc_node+0x18e/0x720
[<0000000024f0534b>] __kmalloc+0x57/0x240
[<000000002930a28e>] __trace_eprobe_create+0x1214/0x1d30
[<0000000028387903>] trace_probe_create+0xf6/0x110
[<00000000a80d6a9f>] eprobe_dyn_event_create+0x21/0x30
[<000000007168698c>] create_dyn_event+0xf3/0x1a0
[<00000000f036bf6a>] trace_parse_run_command+0x1a9/0x2e0
[<00000000014bde8b>] dyn_event_write+0x39/0x50
[<0000000078a097f7>] vfs_write+0x311/0xe50
[<00000000996cb208>] ksys_write+0x158/0x2a0
[<00000000a3c2acb0>] __x64_sys_write+0x7c/0xc0
[<0000000006b5d698>] do_syscall_64+0x60/0x90
[<00000000780e8ecf>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
Fix both issues by releasing the filter string in
trace_event_probe_cleanup().
Link: https://lore.kernel.org/all/20221108235738.1021467-1-rafaelmendsr@gmail.com/
Fixes: 752be5c5c910 ("tracing/eprobe: Add eprobe filter support")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.