On Thu, 26 Apr 2018 09:19:59 +0200 Thomas Richter tmricht@linux.ibm.com wrote:
File /sys/kernel/debug/kprobes/blacklist displays random addresses:
[root@s8360046 linux]# cat /sys/kernel/debug/kprobes/blacklist 0x0000000047149a90-0x00000000bfcb099a print_type_x8 ....
This breaks 'perf probe' which uses the blacklist file to prohibit probes on certain functions by checking the address range.
Fix this by printing the correct (unhashed) address.
Yeah, but I'm not sure recent "%px" policy. I think if the user can dump kallsyms, this also can be dumped. But kallsyms seems different policy...
Anyway, please check my series.
https://patchwork.kernel.org/patch/10183629/
It uses to check the kallsyms policy function to check.
Unfortunately, this is not merged. Anyway, I'll repost it (on the top of tip tree)
The file mode is read all but this is not an issue as the file hierarchy points out: # ls -ld /sys/ /sys/kernel/ /sys/kernel/debug/ /sys/kernel/debug/kprobes/ /sys/kernel/debug/kprobes/blacklist dr-xr-xr-x 12 root root 0 Apr 19 07:56 /sys/ drwxr-xr-x 8 root root 0 Apr 19 07:56 /sys/kernel/ drwx------ 16 root root 0 Apr 19 06:56 /sys/kernel/debug/ drwxr-xr-x 2 root root 0 Apr 19 06:56 /sys/kernel/debug/kprobes/ -r--r--r-- 1 root root 0 Apr 19 06:56 /sys/kernel/debug/kprobes/blacklist
Everything in and below /sys/kernel/debug is rwx to root only, no group or others have access.
Background: Directory /sys/kernel/debug/kprobes is created by debugfs_create_dir() which sets the mode bits to rwxr-xr-x. Maybe change that to use the parent's directory mode bits instead?
Good catch! Yes, it should be hardened. Anyway, that is out of this topic. I just change blacklist file mode bits in my series.
Thank you,
Fixes: ad67b74d2469 ("printk: hash addresses printed with %p") Cc: stable@vger.kernel.org # v4.15+ Cc: linux-kernel@vger.kernel.org To: Ananth N Mavinakayanahalli ananth@linux.vnet.ibm.com To: Anil S Keshavamurthy anil.s.keshavamurthy@intel.com To: David S Miller davem@davemloft.net To: Masami Hiramatsu mhiramat@kernel.org To: Andrew Morton akpm@linux-foundation.org To: acme@kernel.org To: Steven Rostedt rostedt@goodmis.org
Signed-off-by: Thomas Richter tmricht@linux.ibm.com
kernel/kprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 102160ff5c66..ea619021d901 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -2428,7 +2428,7 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v) struct kprobe_blacklist_entry *ent = list_entry(v, struct kprobe_blacklist_entry, list);
- seq_printf(m, "0x%p-0x%p\t%ps\n", (void *)ent->start_addr,
- seq_printf(m, "0x%px-0x%px\t%ps\n", (void *)ent->start_addr, (void *)ent->end_addr, (void *)ent->start_addr); return 0;
}
2.14.3