From ccea8727dc27d8f46df6557f9260ab32760ef409 Mon Sep 17 00:00:00 2001 From: Ravi Bangoria Date: Mon, 20 Aug 2018 10:12:49 +0530 Subject: [PATCH] trace_uprobe/sdt: Prevent multiple reference counter for same uprobe We assume to have only one reference counter for one uprobe. Don't allow user to add multiple trace_uprobe entries having same inode+offset but different reference counter. Ex, # echo "p:sdt_tick/loop2 /home/ravi/tick:0x6e4(0x10036)" > uprobe_events # echo "p:sdt_tick/loop2_1 /home/ravi/tick:0x6e4(0xfffff)" >> uprobe_events bash: echo: write error: Invalid argument # dmesg trace_kprobe: Reference counter offset mismatch. There is one exception though: When user is trying to replace the old entry with the new one, we allow this if the new entry does not conflict with any other existing entries. Link: http://lkml.kernel.org/r/20180820044250.11659-4-ravi.bangoria@linux.ibm.com Acked-by: Srikar Dronamraju Reviewed-by: Song Liu Reviewed-by: Oleg Nesterov Tested-by: Song Liu Signed-off-by: Ravi Bangoria Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_uprobe.c | 37 +++++++++++++++++++++++++++++++++++-- 1 file changed, 35 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 7b85172beab6..3a7c73c40007 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -312,6 +312,35 @@ static int unregister_trace_uprobe(struct trace_uprobe *tu) return 0; } +/* + * Uprobe with multiple reference counter is not allowed. i.e. + * If inode and offset matches, reference counter offset *must* + * match as well. Though, there is one exception: If user is + * replacing old trace_uprobe with new one(same group/event), + * then we allow same uprobe with new reference counter as far + * as the new one does not conflict with any other existing + * ones. + */ +static struct trace_uprobe *find_old_trace_uprobe(struct trace_uprobe *new) +{ + struct trace_uprobe *tmp, *old = NULL; + struct inode *new_inode = d_real_inode(new->path.dentry); + + old = find_probe_event(trace_event_name(&new->tp.call), + new->tp.call.class->system); + + list_for_each_entry(tmp, &uprobe_list, list) { + if ((old ? old != tmp : true) && + new_inode == d_real_inode(tmp->path.dentry) && + new->offset == tmp->offset && + new->ref_ctr_offset != tmp->ref_ctr_offset) { + pr_warn("Reference counter offset mismatch."); + return ERR_PTR(-EINVAL); + } + } + return old; +} + /* Register a trace_uprobe and probe_event */ static int register_trace_uprobe(struct trace_uprobe *tu) { @@ -321,8 +350,12 @@ static int register_trace_uprobe(struct trace_uprobe *tu) mutex_lock(&uprobe_lock); /* register as an event */ - old_tu = find_probe_event(trace_event_name(&tu->tp.call), - tu->tp.call.class->system); + old_tu = find_old_trace_uprobe(tu); + if (IS_ERR(old_tu)) { + ret = PTR_ERR(old_tu); + goto end; + } + if (old_tu) { /* delete old event */ ret = unregister_trace_uprobe(old_tu);