From 9511bce9fe8e5e6c0f923c09243a713eba560141 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Tue, 17 Apr 2018 23:29:07 -0700 Subject: [PATCH] perf/core: Fix bad use of igrab() 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 the issue in kernel/event/core.c. Reviewed-and-tested-by: Alexander Shishkin Reported-by: Miklos Szeredi Signed-off-by: Song Liu Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Fixes: 375637bc5249 ("perf/core: Introduce address range filtering") Link: http://lkml.kernel.org/r/20180418062907.3210386-2-songliubraving@fb.com Signed-off-by: Ingo Molnar --- arch/x86/events/intel/pt.c | 4 ++-- include/linux/perf_event.h | 2 +- kernel/events/core.c | 21 +++++++++------------ 3 files changed, 12 insertions(+), 15 deletions(-) diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 3b993942a0e4..8d016ce5b80d 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -1194,7 +1194,7 @@ static int pt_event_addr_filters_validate(struct list_head *filters) filter->action == PERF_ADDR_FILTER_ACTION_START) return -EOPNOTSUPP; - if (!filter->inode) { + if (!filter->path.dentry) { if (!valid_kernel_ip(filter->offset)) return -EINVAL; @@ -1221,7 +1221,7 @@ static void pt_event_addr_filters_sync(struct perf_event *event) return; list_for_each_entry(filter, &head->list, entry) { - if (filter->inode && !offs[range]) { + if (filter->path.dentry && !offs[range]) { msr_a = msr_b = 0; } else { /* apply the offset */ diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index def866f7269b..bea0b0cd4bf7 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -467,7 +467,7 @@ enum perf_addr_filter_action_t { */ struct perf_addr_filter { struct list_head entry; - struct inode *inode; + struct path path; unsigned long offset; unsigned long size; enum perf_addr_filter_action_t action; diff --git a/kernel/events/core.c b/kernel/events/core.c index ce6aa5ff3c96..24dea13a27ed 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6668,7 +6668,7 @@ static void perf_event_addr_filters_exec(struct perf_event *event, void *data) raw_spin_lock_irqsave(&ifh->lock, flags); list_for_each_entry(filter, &ifh->list, entry) { - if (filter->inode) { + if (filter->path.dentry) { event->addr_filters_offs[count] = 0; restart++; } @@ -7333,7 +7333,7 @@ static bool perf_addr_filter_match(struct perf_addr_filter *filter, struct file *file, unsigned long offset, unsigned long size) { - if (filter->inode != file_inode(file)) + if (d_inode(filter->path.dentry) != file_inode(file)) return false; if (filter->offset > offset + size) @@ -8686,8 +8686,7 @@ static void free_filters_list(struct list_head *filters) struct perf_addr_filter *filter, *iter; list_for_each_entry_safe(filter, iter, filters, entry) { - if (filter->inode) - iput(filter->inode); + path_put(&filter->path); list_del(&filter->entry); kfree(filter); } @@ -8784,7 +8783,7 @@ static void perf_event_addr_filters_apply(struct perf_event *event) * Adjust base offset if the filter is associated to a binary * that needs to be mapped: */ - if (filter->inode) + if (filter->path.dentry) event->addr_filters_offs[count] = perf_addr_filter_apply(filter, mm); @@ -8858,7 +8857,6 @@ perf_event_parse_addr_filter(struct perf_event *event, char *fstr, { struct perf_addr_filter *filter = NULL; char *start, *orig, *filename = NULL; - struct path path; substring_t args[MAX_OPT_ARGS]; int state = IF_STATE_ACTION, token; unsigned int kernel = 0; @@ -8971,19 +8969,18 @@ perf_event_parse_addr_filter(struct perf_event *event, char *fstr, goto fail_free_name; /* look up the path and grab its inode */ - ret = kern_path(filename, LOOKUP_FOLLOW, &path); + ret = kern_path(filename, LOOKUP_FOLLOW, + &filter->path); if (ret) goto fail_free_name; - filter->inode = igrab(d_inode(path.dentry)); - path_put(&path); kfree(filename); filename = NULL; ret = -EINVAL; - if (!filter->inode || - !S_ISREG(filter->inode->i_mode)) - /* free_filters_list() will iput() */ + if (!filter->path.dentry || + !S_ISREG(d_inode(filter->path.dentry) + ->i_mode)) goto fail; event->addr_filters.nr_file_filters++; -- 2.20.1