Tracing fixes: - Fix a deadloop in reading trace_pipe that was caused by a mismatch between ring_buffer_empty() returning false which then asked to read the data, but the read code uses rb_num_of_entries() that returned zero, and causing an infinite "retry".
- Fix a warning caused by not using all pages allocated to store ftrace functions, where this can happen if the linker inserts a bunch of "NULL" entries, causing the accounting of how many pages needed to be off.
- Fix memory leak in freeing iter->temp in tracing_release_pipe().
Linus Torvalds (1): ftrace: Store the order of pages allocated in ftrace_page
Zheng Yejian (3): ring-buffer: Fix deadloop issue on reading trace_pipe tracing: Fix memory leak of iter->temp when reading trace_pipe ftrace: Fix possible warning on checking all pages used in ftrace_process_locs()
kernel/trace/ftrace.c | 72 +++++++++++++++++++++++--------------- kernel/trace/ring_buffer.c | 24 ++++++++----- kernel/trace/trace.c | 1 + 3 files changed, 60 insertions(+), 37 deletions(-)
mainline inclusion from mainline-v6.5-rc2 commit 7e42907f3a7b4ce3a2d1757f6d78336984daf8f5 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I7KXY9
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
---------------------------
Soft lockup occurs when reading file 'trace_pipe':
watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [cat:4488] [...] RIP: 0010:ring_buffer_empty_cpu+0xed/0x170 RSP: 0018:ffff88810dd6fc48 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000246 RCX: ffffffff93d1aaeb RDX: ffff88810a280040 RSI: 0000000000000008 RDI: ffff88811164b218 RBP: ffff88811164b218 R08: 0000000000000000 R09: ffff88815156600f R10: ffffed102a2acc01 R11: 0000000000000001 R12: 0000000051651901 R13: 0000000000000000 R14: ffff888115e49500 R15: 0000000000000000 [...] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8d853c2000 CR3: 000000010dcd8000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __find_next_entry+0x1a8/0x4b0 ? peek_next_entry+0x250/0x250 ? down_write+0xa5/0x120 ? down_write_killable+0x130/0x130 trace_find_next_entry_inc+0x3b/0x1d0 tracing_read_pipe+0x423/0xae0 ? tracing_splice_read_pipe+0xcb0/0xcb0 vfs_read+0x16b/0x490 ksys_read+0x105/0x210 ? __ia32_sys_pwrite64+0x200/0x200 ? switch_fpu_return+0x108/0x220 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x61/0xc6
Through the vmcore, I found it's because in tracing_read_pipe(), ring_buffer_empty_cpu() found some buffer is not empty but then it cannot read anything due to "rb_num_of_entries() == 0" always true, Then it infinitely loop the procedure due to user buffer not been filled, see following code path:
tracing_read_pipe() { ... ... waitagain: tracing_wait_pipe() // 1. find non-empty buffer here trace_find_next_entry_inc() // 2. loop here try to find an entry __find_next_entry() ring_buffer_empty_cpu(); // 3. find non-empty buffer peek_next_entry() // 4. but peek always return NULL ring_buffer_peek() rb_buffer_peek() rb_get_reader_page() // 5. because rb_num_of_entries() == 0 always true here // then return NULL // 6. user buffer not been filled so goto 'waitgain' // and eventually leads to an deadloop in kernel!!! }
By some analyzing, I found that when resetting ringbuffer, the 'entries' of its pages are not all cleared (see rb_reset_cpu()). Then when reducing the ringbuffer, and if some reduced pages exist dirty 'entries' data, they will be added into 'cpu_buffer->overrun' (see rb_remove_pages()), which cause wrong 'overrun' count and eventually cause the deadloop issue.
To fix it, we need to clear every pages in rb_reset_cpu().
Link: https://lore.kernel.org/linux-trace-kernel/20230708225144.3785600-1-zhengyej...
Cc: stable@vger.kernel.org Fixes: a5fb833172eca ("ring-buffer: Fix uninitialized read_stamp") Signed-off-by: Zheng Yejian zhengyejian1@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/ring_buffer.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 23ebe325307d..2aaae6ceccbe 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4922,28 +4922,34 @@ unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu) } EXPORT_SYMBOL_GPL(ring_buffer_size);
+static void rb_clear_buffer_page(struct buffer_page *page) +{ + local_set(&page->write, 0); + local_set(&page->entries, 0); + rb_init_page(page->page); + page->read = 0; +} + static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) { + struct buffer_page *page; + rb_head_page_deactivate(cpu_buffer);
cpu_buffer->head_page = list_entry(cpu_buffer->pages, struct buffer_page, list); - local_set(&cpu_buffer->head_page->write, 0); - local_set(&cpu_buffer->head_page->entries, 0); - local_set(&cpu_buffer->head_page->page->commit, 0); - - cpu_buffer->head_page->read = 0; + rb_clear_buffer_page(cpu_buffer->head_page); + list_for_each_entry(page, cpu_buffer->pages, list) { + rb_clear_buffer_page(page); + }
cpu_buffer->tail_page = cpu_buffer->head_page; cpu_buffer->commit_page = cpu_buffer->head_page;
INIT_LIST_HEAD(&cpu_buffer->reader_page->list); INIT_LIST_HEAD(&cpu_buffer->new_pages); - local_set(&cpu_buffer->reader_page->write, 0); - local_set(&cpu_buffer->reader_page->entries, 0); - local_set(&cpu_buffer->reader_page->page->commit, 0); - cpu_buffer->reader_page->read = 0; + rb_clear_buffer_page(cpu_buffer->reader_page);
local_set(&cpu_buffer->entries_bytes, 0); local_set(&cpu_buffer->overrun, 0);
mainline inclusion from mainline-v6.5-rc2 commit d5a821896360cc8b93a15bd888fabc858c038dc0 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I7L517
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
--------------------------------
kmemleak reports: unreferenced object 0xffff88814d14e200 (size 256): comm "cat", pid 336, jiffies 4294871818 (age 779.490s) hex dump (first 32 bytes): 04 00 01 03 00 00 00 00 08 00 00 00 00 00 00 00 ................ 0c d8 c8 9b ff ff ff ff 04 5a ca 9b ff ff ff ff .........Z...... backtrace: [<ffffffff9bdff18f>] __kmalloc+0x4f/0x140 [<ffffffff9bc9238b>] trace_find_next_entry+0xbb/0x1d0 [<ffffffff9bc9caef>] trace_print_lat_context+0xaf/0x4e0 [<ffffffff9bc94490>] print_trace_line+0x3e0/0x950 [<ffffffff9bc95499>] tracing_read_pipe+0x2d9/0x5a0 [<ffffffff9bf03a43>] vfs_read+0x143/0x520 [<ffffffff9bf04c2d>] ksys_read+0xbd/0x160 [<ffffffff9d0f0edf>] do_syscall_64+0x3f/0x90 [<ffffffff9d2000aa>] entry_SYSCALL_64_after_hwframe+0x6e/0xd8
when reading file 'trace_pipe', 'iter->temp' is allocated or relocated in trace_find_next_entry() but not freed before 'trace_pipe' is closed.
To fix it, free 'iter->temp' in tracing_release_pipe().
Link: https://lore.kernel.org/linux-trace-kernel/20230713141435.1133021-1-zhengyej...
Cc: stable@vger.kernel.org Fixes: ff895103a84ab ("tracing: Save off entry when peeking at next entry") Signed-off-by: Zheng Yejian zhengyejian1@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Zheng Yejian zhengyejian1@huawei.com --- kernel/trace/trace.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index e5eef18a11d9..7f1226aefab4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6259,6 +6259,7 @@ static int tracing_release_pipe(struct inode *inode, struct file *file) mutex_unlock(&trace_types_lock);
free_cpumask_var(iter->started); + kfree(iter->temp); mutex_destroy(&iter->mutex); kfree(iter);
From: Linus Torvalds torvalds@linux-foundation.org
mainline inclusion from mainline-v5.13-rc1 commit db42523b4f3e83ff86b53cdda219a9767c8b047f category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I7KYPM
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
--------------------------------
Instead of saving the size of the records field of the ftrace_page, store the order it uses to allocate the pages, as that is what is needed to know in order to free the pages. This simplifies the code.
Link: https://lore.kernel.org/lkml/CAHk-=whyMxheOqXAORt9a7JK9gc9eHTgCJ55Pgs4p=X3Rr...
Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [ change log written by Steven Rostedt ] Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Zheng Yejian zhengyejian1@huawei.com --- kernel/trace/ftrace.c | 35 +++++++++++++++++------------------ 1 file changed, 17 insertions(+), 18 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 0b44a2f147eb..a8f74aea1dba 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1092,7 +1092,7 @@ struct ftrace_page { struct ftrace_page *next; struct dyn_ftrace *records; int index; - int size; + int order; };
#define ENTRY_SIZE sizeof(struct dyn_ftrace) @@ -3188,7 +3188,7 @@ static int ftrace_allocate_records(struct ftrace_page *pg, int count) ftrace_number_of_groups++;
cnt = (PAGE_SIZE << order) / ENTRY_SIZE; - pg->size = cnt; + pg->order = order;
if (cnt > count) cnt = count; @@ -3201,7 +3201,6 @@ ftrace_allocate_pages(unsigned long num_to_init) { struct ftrace_page *start_pg; struct ftrace_page *pg; - int order; int cnt;
if (!num_to_init) @@ -3237,13 +3236,13 @@ ftrace_allocate_pages(unsigned long num_to_init) free_pages: pg = start_pg; while (pg) { - order = get_count_order(pg->size / ENTRIES_PER_PAGE); - if (order >= 0) - free_pages((unsigned long)pg->records, order); + if (pg->records) { + free_pages((unsigned long)pg->records, pg->order); + ftrace_number_of_pages -= 1 << pg->order; + } start_pg = pg->next; kfree(pg); pg = start_pg; - ftrace_number_of_pages -= 1 << order; ftrace_number_of_groups--; } pr_info("ftrace: FAILED to allocate memory for functions\n"); @@ -6239,6 +6238,7 @@ static int ftrace_process_locs(struct module *mod, p = start; pg = start_pg; while (p < end) { + unsigned long end_offset; addr = ftrace_call_adjust(*p++); /* * Some architecture linkers will pad between @@ -6249,7 +6249,8 @@ static int ftrace_process_locs(struct module *mod, if (!addr) continue;
- if (pg->index == pg->size) { + end_offset = (pg->index+1) * sizeof(pg->records[0]); + if (end_offset > PAGE_SIZE << pg->order) { /* We should have allocated enough */ if (WARN_ON(!pg->next)) break; @@ -6418,7 +6419,6 @@ void ftrace_release_mod(struct module *mod) struct ftrace_page **last_pg; struct ftrace_page *tmp_page = NULL; struct ftrace_page *pg; - int order;
mutex_lock(&ftrace_lock);
@@ -6469,12 +6469,12 @@ void ftrace_release_mod(struct module *mod) /* Needs to be called outside of ftrace_lock */ clear_mod_from_hashes(pg);
- order = get_count_order(pg->size / ENTRIES_PER_PAGE); - if (order >= 0) - free_pages((unsigned long)pg->records, order); + if (pg->records) { + free_pages((unsigned long)pg->records, pg->order); + ftrace_number_of_pages -= 1 << pg->order; + } tmp_page = pg->next; kfree(pg); - ftrace_number_of_pages -= 1 << order; ftrace_number_of_groups--; } } @@ -6792,7 +6792,6 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr) struct ftrace_mod_map *mod_map = NULL; struct ftrace_init_func *func, *func_next; struct list_head clear_hash; - int order;
INIT_LIST_HEAD(&clear_hash);
@@ -6830,10 +6829,10 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr) ftrace_update_tot_cnt--; if (!pg->index) { *last_pg = pg->next; - order = get_count_order(pg->size / ENTRIES_PER_PAGE); - if (order >= 0) - free_pages((unsigned long)pg->records, order); - ftrace_number_of_pages -= 1 << order; + if (pg->records) { + free_pages((unsigned long)pg->records, pg->order); + ftrace_number_of_pages -= 1 << pg->order; + } ftrace_number_of_groups--; kfree(pg); pg = container_of(last_pg, struct ftrace_page, next);
mainline inclusion from mainline-v6.5-rc2 commit 26efd79c4624294e553aeaa3439c646729bad084 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I7KYPM
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
--------------------------------
As comments in ftrace_process_locs(), there may be NULL pointers in mcount_loc section:
Some architecture linkers will pad between the different mcount_loc sections of different object files to satisfy alignments. Skip any NULL pointers.
After commit 20e5227e9f55 ("ftrace: allow NULL pointers in mcount_loc"), NULL pointers will be accounted when allocating ftrace pages but skipped before adding into ftrace pages, this may result in some pages not being used. Then after commit 706c81f87f84 ("ftrace: Remove extra helper functions"), warning may occur at: WARN_ON(pg->next);
To fix it, only warn for case that no pointers skipped but pages not used up, then free those unused pages after releasing ftrace_lock.
Link: https://lore.kernel.org/linux-trace-kernel/20230712060452.3175675-1-zhengyej...
Cc: stable@vger.kernel.org Fixes: 706c81f87f84 ("ftrace: Remove extra helper functions") Suggested-by: Steven Rostedt rostedt@goodmis.org Signed-off-by: Zheng Yejian zhengyejian1@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/ftrace.c | 45 +++++++++++++++++++++++++++++-------------- 1 file changed, 31 insertions(+), 14 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index a8f74aea1dba..b733b7cc5a7e 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3196,6 +3196,22 @@ static int ftrace_allocate_records(struct ftrace_page *pg, int count) return cnt; }
+static void ftrace_free_pages(struct ftrace_page *pages) +{ + struct ftrace_page *pg = pages; + + while (pg) { + if (pg->records) { + free_pages((unsigned long)pg->records, pg->order); + ftrace_number_of_pages -= 1 << pg->order; + } + pages = pg->next; + kfree(pg); + pg = pages; + ftrace_number_of_groups--; + } +} + static struct ftrace_page * ftrace_allocate_pages(unsigned long num_to_init) { @@ -3234,17 +3250,7 @@ ftrace_allocate_pages(unsigned long num_to_init) return start_pg;
free_pages: - pg = start_pg; - while (pg) { - if (pg->records) { - free_pages((unsigned long)pg->records, pg->order); - ftrace_number_of_pages -= 1 << pg->order; - } - start_pg = pg->next; - kfree(pg); - pg = start_pg; - ftrace_number_of_groups--; - } + ftrace_free_pages(start_pg); pr_info("ftrace: FAILED to allocate memory for functions\n"); return NULL; } @@ -6190,9 +6196,11 @@ static int ftrace_process_locs(struct module *mod, unsigned long *start, unsigned long *end) { + struct ftrace_page *pg_unuse = NULL; struct ftrace_page *start_pg; struct ftrace_page *pg; struct dyn_ftrace *rec; + unsigned long skipped = 0; unsigned long count; unsigned long *p; unsigned long addr; @@ -6246,8 +6254,10 @@ static int ftrace_process_locs(struct module *mod, * object files to satisfy alignments. * Skip any NULL pointers. */ - if (!addr) + if (!addr) { + skipped++; continue; + }
end_offset = (pg->index+1) * sizeof(pg->records[0]); if (end_offset > PAGE_SIZE << pg->order) { @@ -6261,8 +6271,10 @@ static int ftrace_process_locs(struct module *mod, rec->ip = addr; }
- /* We should have used all pages */ - WARN_ON(pg->next); + if (pg->next) { + pg_unuse = pg->next; + pg->next = NULL; + }
/* Assign the last page to ftrace_pages */ ftrace_pages = pg; @@ -6284,6 +6296,11 @@ static int ftrace_process_locs(struct module *mod, out: mutex_unlock(&ftrace_lock);
+ /* We should have used all pages unless we skipped some */ + if (pg_unuse) { + WARN_ON(!skipped); + ftrace_free_pages(pg_unuse); + } return ret; }
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