commit 0c92c7a3c5d416f47b32c5f20a611dfeca5d5f2e upstream.
As Miklos reported and suggested:
This pattern repeats two times in trace_uprobe.c and in kernel/events/core.c as well:
ret = kern_path(filename, LOOKUP_FOLLOW, &path); if (ret) goto fail_address_parse;
inode = igrab(d_inode(path.dentry)); path_put(&path);
And it's wrong. You can only hold a reference to the inode if you have an active ref to the superblock as well (which is normally through path.mnt) or holding s_umount.
This way unmounting the containing filesystem while the tracepoint is active will give you the "VFS: Busy inodes after unmount..." message and a crash when the inode is finally put.
Solution: store path instead of inode.
This patch fixes two instances in trace_uprobe.c. struct path is added to struct trace_uprobe to keep the inode and containing mount point referenced.
Link: http://lkml.kernel.org/r/20180423172135.4050588-1-songliubraving@fb.com
Fixes: f3f096cfedf8 ("tracing: Provide trace events interface for uprobes") Fixes: 33ea4b24277b ("perf/core: Implement the 'perf_uprobe' PMU") Cc: stable@vger.kernel.org #4.14+ Cc: Ingo Molnar mingo@redhat.com Cc: Howard McLauchlan hmclauchlan@fb.com Cc: Josef Bacik jbacik@fb.com Cc: Srikar Dronamraju srikar@linux.vnet.ibm.com Cc: Steven Rostedt (VMware) rostedt@goodmis.org Acked-by: Miklos Szeredi mszeredi@redhat.com Reported-by: Miklos Szeredi miklos@szeredi.hu Signed-off-by: Song Liu songliubraving@fb.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- kernel/trace/trace_uprobe.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 4525e02..14d3af6 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -55,6 +55,7 @@ struct trace_uprobe { struct list_head list; struct trace_uprobe_filter filter; struct uprobe_consumer consumer; + struct path path; struct inode *inode; char *filename; unsigned long offset; @@ -287,7 +288,7 @@ static void free_trace_uprobe(struct trace_uprobe *tu) for (i = 0; i < tu->tp.nr_args; i++) traceprobe_free_probe_arg(&tu->tp.args[i]);
- iput(tu->inode); + path_put(&tu->path); kfree(tu->tp.call.class->system); kfree(tu->tp.call.name); kfree(tu->filename); @@ -361,7 +362,6 @@ static int register_trace_uprobe(struct trace_uprobe *tu) static int create_trace_uprobe(int argc, char **argv) { struct trace_uprobe *tu; - struct inode *inode; char *arg, *event, *group, *filename; char buf[MAX_EVENT_NAME_LEN]; struct path path; @@ -369,7 +369,6 @@ static int create_trace_uprobe(int argc, char **argv) bool is_delete, is_return; int i, ret;
- inode = NULL; ret = 0; is_delete = false; is_return = false; @@ -435,21 +434,16 @@ static int create_trace_uprobe(int argc, char **argv) } /* Find the last occurrence, in case the path contains ':' too. */ arg = strrchr(argv[1], ':'); - if (!arg) { - ret = -EINVAL; - goto fail_address_parse; - } + if (!arg) + return -EINVAL;
*arg++ = '\0'; filename = argv[1]; ret = kern_path(filename, LOOKUP_FOLLOW, &path); if (ret) - goto fail_address_parse; - - inode = igrab(d_inode(path.dentry)); - path_put(&path); + return ret;
- if (!inode || !S_ISREG(inode->i_mode)) { + if (!d_is_reg(path.dentry)) { ret = -EINVAL; goto fail_address_parse; } @@ -488,7 +482,7 @@ static int create_trace_uprobe(int argc, char **argv) goto fail_address_parse; } tu->offset = offset; - tu->inode = inode; + tu->path = path; tu->filename = kstrdup(filename, GFP_KERNEL);
if (!tu->filename) { @@ -556,7 +550,7 @@ static int create_trace_uprobe(int argc, char **argv) return ret;
fail_address_parse: - iput(inode); + path_put(&path);
pr_info("Failed to parse address or file.\n");
@@ -935,6 +929,7 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file, goto err_flags;
tu->consumer.filter = filter; + tu->inode = d_real_inode(tu->path.dentry); ret = uprobe_register(tu->inode, tu->offset, &tu->consumer); if (ret) goto err_buffer; @@ -980,6 +975,7 @@ probe_event_disable(struct trace_uprobe *tu, struct trace_event_file *file) WARN_ON(!uprobe_filter_is_empty(&tu->filter));
uprobe_unregister(tu->inode, tu->offset, &tu->consumer); + tu->inode = NULL; tu->tp.flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
uprobe_buffer_disable();