Messages in this thread | | | From | Miklos Szeredi <> | Date | Thu, 19 Apr 2018 16:44:08 +0200 | Subject | Re: [PATCH v2] tracing: fix bad use of igrab in trace_uprobe.c |
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On Thu, Apr 19, 2018 at 10:58 AM, Miklos Szeredi <miklos@szeredi.hu> wrote: > On Wed, Apr 18, 2018 at 7:40 PM, Song Liu <songliubraving@fb.com> wrote: >> 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. >> >> Fixes: f3f096cfedf8 ("tracing: Provide trace events interface for uprobes") >> Fixes: 33ea4b24277b ("perf/core: Implement the 'perf_uprobe' PMU") >> Cc: Steven Rostedt <rostedt@goodmis.org> >> 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> >> Reported-by: Miklos Szeredi <miklos@szeredi.hu> >> Signed-off-by: Song Liu <songliubraving@fb.com> >> --- >> kernel/trace/trace_uprobe.c | 49 +++++++++++++++------------------------------ >> 1 file changed, 16 insertions(+), 33 deletions(-) >> >> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c >> index 34fd0e0..d9ee522c 100644 >> --- a/kernel/trace/trace_uprobe.c >> +++ b/kernel/trace/trace_uprobe.c >> @@ -55,7 +55,7 @@ struct trace_uprobe { >> struct list_head list; >> struct trace_uprobe_filter filter; >> struct uprobe_consumer consumer; >> - struct inode *inode; >> + struct path path; >> char *filename; >> unsigned long offset; >> unsigned long nhit; >> @@ -289,7 +289,7 @@ 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); >> @@ -363,7 +363,6 @@ 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; >> @@ -371,7 +370,6 @@ 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; >> @@ -437,24 +435,14 @@ 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_real_inode(path.dentry));
Also, where has the d_real_inode() gone?
Looks like we need tu->inode back, since the return value of d_real_inode() may change over time. I'd do the "tu->inode = d_real_inode(tu->path.dentry)" just before first use (i.e. when enabling the tracepoint).
Thanks, Miklos
>> - path_put(&path); >> - >> - if (!inode || !S_ISREG(inode->i_mode)) { > > Where has the S_ISREG check gone? > >> - ret = -EINVAL; >> - goto fail_address_parse; >> - } >> + return ret; >> >> ret = kstrtoul(arg, 0, &offset); >> if (ret) >> @@ -490,7 +478,7 @@ 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) { >> @@ -558,7 +546,7 @@ 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"); >> >> @@ -922,7 +910,8 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file, >> goto err_flags; >> >> tu->consumer.filter = filter; >> - ret = uprobe_register(tu->inode, tu->offset, &tu->consumer); >> + ret = uprobe_register(d_inode(tu->path.dentry), tu->offset, >> + &tu->consumer); >> if (ret) >> goto err_buffer; >> >> @@ -966,7 +955,7 @@ 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); >> + uprobe_unregister(d_inode(tu->path.dentry), tu->offset, &tu->consumer); >> tu->tp.flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE; >> >> uprobe_buffer_disable(); >> @@ -1041,7 +1030,8 @@ static int uprobe_perf_close(struct trace_uprobe *tu, struct perf_event *event) >> write_unlock(&tu->filter.rwlock); >> >> if (!done) >> - return uprobe_apply(tu->inode, tu->offset, &tu->consumer, false); >> + return uprobe_apply(d_inode(tu->path.dentry), tu->offset, >> + &tu->consumer, false); >> >> return 0; >> } >> @@ -1073,7 +1063,8 @@ static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event) >> >> err = 0; >> if (!done) { >> - err = uprobe_apply(tu->inode, tu->offset, &tu->consumer, true); >> + err = uprobe_apply(d_inode(tu->path.dentry), >> + tu->offset, &tu->consumer, true); >> if (err) >> uprobe_perf_close(tu, event); >> } >> @@ -1337,7 +1328,6 @@ struct trace_event_call * >> create_local_trace_uprobe(char *name, unsigned long offs, bool is_return) >> { >> struct trace_uprobe *tu; >> - struct inode *inode; >> struct path path; >> int ret; >> >> @@ -1345,14 +1335,6 @@ create_local_trace_uprobe(char *name, unsigned long offs, bool is_return) >> if (ret) >> return ERR_PTR(ret); >> >> - inode = igrab(d_inode(path.dentry)); >> - path_put(&path); >> - >> - if (!inode || !S_ISREG(inode->i_mode)) { > > And here, again. > > Otherwise ACK. > > Also please create a separate patch that removes igrab/iput calls from > kernel/events/uprobes.c and adds a comment to the effect that the > caller is required to keep the inode (and the containing mount) > referenced. > > Thanks, > Miklos
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