There are many of those warnings. In file included from ./arch/powerpc/include/asm/paca.h:15, from ./arch/powerpc/include/asm/current.h:13, from ./include/linux/thread_info.h:21, from ./include/asm-generic/preempt.h:5, from ./arch/powerpc/include/generated/asm/preempt.h:1, from ./include/linux/preempt.h:78, from ./include/linux/spinlock.h:51, from fs/fs-writeback.c:19: In function 'strncpy', inlined from 'perf_trace_writeback_page_template' at ./include/trace/events/writeback.h:56:1: ./include/linux/string.h:260:9: warning: '__builtin_strncpy' specified bound 32 equals destination size [-Wstringop-truncation] return __builtin_strncpy(p, q, size); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fix it by using the new strscpy_pad() which was introduced in the commit 458a3bf82df4 ("lib/string: Add strscpy_pad() function") and will always be NUL-terminated instead of strncpy(). Also, changes strlcpy() to use strscpy_pad() in this file for consistency. Fixes: 455b2864686d ("writeback: Initial tracing support") Fixes: 028c2dd184c0 ("writeback: Add tracing to balance_dirty_pages") Fixes: e84d0a4f8e39 ("writeback: trace event writeback_queue_io") Fixes: b48c104d2211 ("writeback: trace event bdi_dirty_ratelimit") Fixes: cc1676d917f3 ("writeback: Move requeueing when I_SYNC set to writeback_sb_inodes()") Fixes: 9fb0a7da0c52 ("writeback: add more tracepoints") Signed-off-by: Qian Cai <c...@lca.pw> --- v3: Rearrange a long-line a bit to make the code more readable. v2: Use strscpy_pad() to address the possible data leaking concern from Steve [1]. Replace strlcpy() as well for consistency. [1] https://lore.kernel.org/lkml/20190716170339.1c447...@gandalf.local.home/ include/trace/events/writeback.h | 38 ++++++++++++++++++++------------------ 1 file changed, 20 insertions(+), 18 deletions(-) diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index aa7f3aeac740..79095434c1be 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -66,8 +66,9 @@ ), TP_fast_assign( - strncpy(__entry->name, - mapping ? dev_name(inode_to_bdi(mapping->host)->dev) : "(unknown)", 32); + strscpy_pad(__entry->name, + mapping ? dev_name(inode_to_bdi(mapping->host)->dev) : "(unknown)", + 32); __entry->ino = mapping ? mapping->host->i_ino : 0; __entry->index = page->index; ), @@ -110,8 +111,8 @@ struct backing_dev_info *bdi = inode_to_bdi(inode); /* may be called for files on pseudo FSes w/ unregistered bdi */ - strncpy(__entry->name, - bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32); + strscpy_pad(__entry->name, + bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32); __entry->ino = inode->i_ino; __entry->state = inode->i_state; __entry->flags = flags; @@ -190,8 +191,8 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w ), TP_fast_assign( - strncpy(__entry->name, - dev_name(inode_to_bdi(inode)->dev), 32); + strscpy_pad(__entry->name, + dev_name(inode_to_bdi(inode)->dev), 32); __entry->ino = inode->i_ino; __entry->sync_mode = wbc->sync_mode; __entry->cgroup_ino = __trace_wbc_assign_cgroup(wbc); @@ -234,8 +235,9 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w __field(unsigned int, cgroup_ino) ), TP_fast_assign( - strncpy(__entry->name, - wb->bdi->dev ? dev_name(wb->bdi->dev) : "(unknown)", 32); + strscpy_pad(__entry->name, + wb->bdi->dev ? dev_name(wb->bdi->dev) : + "(unknown)", 32); __entry->nr_pages = work->nr_pages; __entry->sb_dev = work->sb ? work->sb->s_dev : 0; __entry->sync_mode = work->sync_mode; @@ -288,7 +290,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w __field(unsigned int, cgroup_ino) ), TP_fast_assign( - strncpy(__entry->name, dev_name(wb->bdi->dev), 32); + strscpy_pad(__entry->name, dev_name(wb->bdi->dev), 32); __entry->cgroup_ino = __trace_wb_assign_cgroup(wb); ), TP_printk("bdi %s: cgroup_ino=%u", @@ -310,7 +312,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w __array(char, name, 32) ), TP_fast_assign( - strncpy(__entry->name, dev_name(bdi->dev), 32); + strscpy_pad(__entry->name, dev_name(bdi->dev), 32); ), TP_printk("bdi %s", __entry->name @@ -335,7 +337,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w ), TP_fast_assign( - strncpy(__entry->name, dev_name(bdi->dev), 32); + strscpy_pad(__entry->name, dev_name(bdi->dev), 32); __entry->nr_to_write = wbc->nr_to_write; __entry->pages_skipped = wbc->pages_skipped; __entry->sync_mode = wbc->sync_mode; @@ -386,7 +388,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w ), TP_fast_assign( unsigned long *older_than_this = work->older_than_this; - strncpy(__entry->name, dev_name(wb->bdi->dev), 32); + strscpy_pad(__entry->name, dev_name(wb->bdi->dev), 32); __entry->older = older_than_this ? *older_than_this : 0; __entry->age = older_than_this ? (jiffies - *older_than_this) * 1000 / HZ : -1; @@ -472,7 +474,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w ), TP_fast_assign( - strlcpy(__entry->bdi, dev_name(wb->bdi->dev), 32); + strscpy_pad(__entry->bdi, dev_name(wb->bdi->dev), 32); __entry->write_bw = KBps(wb->write_bandwidth); __entry->avg_write_bw = KBps(wb->avg_write_bandwidth); __entry->dirty_rate = KBps(dirty_rate); @@ -537,7 +539,7 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w TP_fast_assign( unsigned long freerun = (thresh + bg_thresh) / 2; - strlcpy(__entry->bdi, dev_name(wb->bdi->dev), 32); + strscpy_pad(__entry->bdi, dev_name(wb->bdi->dev), 32); __entry->limit = global_wb_domain.dirty_limit; __entry->setpoint = (global_wb_domain.dirty_limit + @@ -597,8 +599,8 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w ), TP_fast_assign( - strncpy(__entry->name, - dev_name(inode_to_bdi(inode)->dev), 32); + strscpy_pad(__entry->name, + dev_name(inode_to_bdi(inode)->dev), 32); __entry->ino = inode->i_ino; __entry->state = inode->i_state; __entry->dirtied_when = inode->dirtied_when; @@ -671,8 +673,8 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w ), TP_fast_assign( - strncpy(__entry->name, - dev_name(inode_to_bdi(inode)->dev), 32); + strscpy_pad(__entry->name, + dev_name(inode_to_bdi(inode)->dev), 32); __entry->ino = inode->i_ino; __entry->state = inode->i_state; __entry->dirtied_when = inode->dirtied_when; -- 1.8.3.1