3.16.60-rc1 review patch. If anyone has any objections, please let me know.
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From: Song Liu songliubraving@fb.com
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: 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 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 [bwh: Backported to 3.16: - Open-code d_real_inode(), d_is_reg() - Drop changes in create_local_trace_uprobe()] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- kernel/trace/trace_uprobe.c | 35 ++++++++++++++--------------------- 1 file changed, 14 insertions(+), 21 deletions(-)
--- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -53,6 +53,7 @@ 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; @@ -284,7 +285,7 @@ static void free_trace_uprobe(struct tra 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); @@ -358,7 +359,6 @@ end: 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; @@ -366,7 +366,6 @@ static int create_trace_uprobe(int argc, bool is_delete, is_return; int i, ret;
- inode = NULL; ret = 0; is_delete = false; is_return = false; @@ -432,21 +431,16 @@ static int create_trace_uprobe(int argc, } /* 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(path.dentry->d_inode); - path_put(&path); + return ret;
- if (!inode || !S_ISREG(inode->i_mode)) { + if (!S_ISREG(path.dentry->d_inode->i_mode)) { ret = -EINVAL; goto fail_address_parse; } @@ -485,7 +479,7 @@ static int create_trace_uprobe(int argc, goto fail_address_parse; } tu->offset = offset; - tu->inode = inode; + tu->path = path; tu->filename = kstrdup(filename, GFP_KERNEL);
if (!tu->filename) { @@ -552,7 +546,7 @@ error: return ret;
fail_address_parse: - iput(inode); + path_put(&path);
pr_info("Failed to parse address or file.\n");
@@ -919,6 +913,7 @@ probe_event_enable(struct trace_uprobe * goto err_flags;
tu->consumer.filter = filter; + tu->inode = tu->path.dentry->d_inode; ret = uprobe_register(tu->inode, tu->offset, &tu->consumer); if (ret) goto err_buffer; @@ -964,6 +959,7 @@ probe_event_disable(struct trace_uprobe 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();