On Fri, 2021-06-25 at 18:05 +0000, Chuck Lever III wrote:
>
>
> > On Jun 25, 2021, at 12:28 PM, Trond Myklebust
> > <trondmy@xxxxxxxxxxxxxxx> wrote:
> >
> > On Fri, 2021-06-25 at 11:12 -0400, Chuck Lever wrote:
> > > The double copy of the string is a mistake, plus __assign_str()
> > > uses strlen(), which is wrong to do on a string that isn't
> > > guaranteed to be NUL-terminated.
> > >
> > > Fixes: 6019ce0742ca ("NFSD: Add a tracepoint to record directory
> > > entry encoding")
> > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > > ---
> > > fs/nfsd/trace.h | 1 -
> > > 1 file changed, 1 deletion(-)
> > >
> > > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > > index 27a93ebd1d80..89dccced526a 100644
> > > --- a/fs/nfsd/trace.h
> > > +++ b/fs/nfsd/trace.h
> > > @@ -408,7 +408,6 @@ TRACE_EVENT(nfsd_dirent,
> > > __entry->ino = ino;
> > > __entry->len = namlen;
> > > memcpy(__get_str(name), name, namlen);
> > > - __assign_str(name, name);
> > > ),
> > > TP_printk("fh_hash=0x%08x ino=%llu name=%.*s",
> > > __entry->fh_hash, __entry->ino,
> > >
> > >
> >
> > Why not just store it as a NUL terminated string and save a few bytes
> > by getting rid of the integer-sized storage of the length?
>
> Stephen is adding some helpers to do that in the next merge
> window. For now, I need to fix this oops, and this is the
> fastest way to do that.
Won't this suffice?
8<---------------------------------------
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 27a93ebd1d80..799168774ccf 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -400,19 +400,17 @@ TRACE_EVENT(nfsd_dirent,
TP_STRUCT__entry(
__field(u32, fh_hash)
__field(u64, ino)
- __field(int, len)
- __dynamic_array(unsigned char, name, namlen)
+ __dynamic_array(unsigned char, name, namlen + 1)
),
TP_fast_assign(
__entry->fh_hash = fhp ? knfsd_fh_hash(&fhp->fh_handle) : 0;
__entry->ino = ino;
- __entry->len = namlen;
memcpy(__get_str(name), name, namlen);
- __assign_str(name, name);
+ __get_str(name)[namlen] = 0;
),
- TP_printk("fh_hash=0x%08x ino=%llu name=%.*s",
+ TP_printk("fh_hash=0x%08x ino=%llu name=%s",
__entry->fh_hash, __entry->ino,
- __entry->len, __get_str(name))
+ __get_str(name))
)
#include "state.h"
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
