On Thu, 2017-03-02 at 23:59 +0100, Arnd Bergmann wrote:
KASAN decides that passing a pointer to _m into an extern function (_mlog_printk) is potentially dangerous, as that function might keep a reference to that pointer after it goes out of scope, or it might not know the correct length of the stack object pointed to.
We can see from looking at the __mlog_printk() function definition that it's actually safe, but the compiler cannot see that when looking at another source file.
OK, thanks.
btw:
changing __mlog_printk can save ~11% (90+KB) of object text size by removing __func__ and __LINE__ and using vsprintf pointer extension %pS, __builtin_return_address(0) as it is already used in dlmmaster.
(defconfig x86-64, with ocfs2)
$ size fs/ocfs2/built-in.o* text data bss dec hex filename 759791 111373 105688 976852 ee7d4 fs/ocfs2/built-in.o.new 852959 111373 105688 1070020 1053c4 fs/ocfs2/built-in.o.old
It's nearly the same output.
---
fs/ocfs2/cluster/masklog.c | 8 ++++---- fs/ocfs2/cluster/masklog.h | 8 +++----- 2 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/fs/ocfs2/cluster/masklog.c b/fs/ocfs2/cluster/masklog.c index d331c2386b94..a3f080f37108 100644 --- a/fs/ocfs2/cluster/masklog.c +++ b/fs/ocfs2/cluster/masklog.c @@ -64,8 +64,7 @@ static ssize_t mlog_mask_store(u64 mask, const char *buf, size_t count) return count; }
-void __mlog_printk(const u64 *mask, const char *func, int line, - const char *fmt, ...) +void __mlog_printk(const u64 *mask, const char *fmt, ...) { struct va_format vaf; va_list args; @@ -90,9 +89,10 @@ void __mlog_printk(const u64 *mask, const char *func, int line, vaf.fmt = fmt; vaf.va = &args;
- printk("%s(%s,%u,%u):%s:%d %s%pV", + printk("%s(%s,%u,%u):%pS %s%pV", level, current->comm, task_pid_nr(current), - raw_smp_processor_id(), func, line, prefix, &vaf); + raw_smp_processor_id(), __builtin_return_address(0), + prefix, &vaf);
va_end(args); } diff --git a/fs/ocfs2/cluster/masklog.h b/fs/ocfs2/cluster/masklog.h index 3c16da69605d..56ba5baf625b 100644 --- a/fs/ocfs2/cluster/masklog.h +++ b/fs/ocfs2/cluster/masklog.h @@ -162,9 +162,8 @@ extern struct mlog_bits mlog_and_bits, mlog_not_bits;
#endif
-__printf(4, 5) __nocapture(2) -void __mlog_printk(const u64 *m, const char *func, int line, - const char *fmt, ...); +__printf(2, 3) __nocapture(2) +void __mlog_printk(const u64 *m, const char *fmt, ...);
/* * Testing before the __mlog_printk call lets the compiler eliminate the @@ -174,8 +173,7 @@ void __mlog_printk(const u64 *m, const char *func, int line, do { \ u64 _m = MLOG_MASK_PREFIX | (mask); \ if (_m & ML_ALLOWED_BITS) \ - __mlog_printk(&_m, __func__, __LINE__, fmt, \ - ##__VA_ARGS__); \ + __mlog_printk(&_m, fmt, ##__VA_ARGS__); \ } while (0)
#define mlog_errno(st) ({ \