| From: Song Liu <songliubraving@fb.com> |
| Date: Mon, 23 Apr 2018 10:21:34 -0700 |
| Subject: tracing: Fix bad use of igrab in trace_uprobe.c |
| |
| 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(); |