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Message-ID: <20190730172248.GL28829@quack2.suse.cz>
Date: Tue, 30 Jul 2019 19:22:48 +0200
From: Jan Kara <jack@...e.cz>
To: Qian Cai <cai@....pw>
Cc: akpm@...ux-foundation.org, tobin@...nel.org, rostedt@...dmis.org,
mingo@...hat.com, tj@...nel.org, dchinner@...hat.com,
fengguang.wu@...el.com, jack@...e.cz, axboe@...nel.dk,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] writeback: fix -Wstringop-truncation warnings
On Thu 25-07-19 13:18:19, Qian Cai wrote:
> 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 <cai@....pw>
Looks good to me. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
>
> 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/20190716170339.1c44719d@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
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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