strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89
Signed-off-by: Azeem Shaikh <[email protected]>
---
fs/nfsd/trace.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 4183819ea082..9b32cda54808 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -1370,7 +1370,7 @@ TRACE_EVENT(nfsd_cb_setup,
TP_fast_assign(
__entry->cl_boot = clp->cl_clientid.cl_boot;
__entry->cl_id = clp->cl_clientid.cl_id;
- strlcpy(__entry->netid, netid, sizeof(__entry->netid));
+ strscpy(__entry->netid, netid, sizeof(__entry->netid));
__entry->authflavor = authflavor;
__assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
clp->cl_cb_conn.cb_addrlen)
Hello Azeem -
> On May 10, 2023, at 3:09 PM, Azeem Shaikh <[email protected]> wrote:
>
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
Actually netid should use the __string() and __assign_str()
macros rather than open-coding a string copy, I think.
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
>
I suggest adding:
Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint")
> Signed-off-by: Azeem Shaikh <[email protected]>
> ---
> fs/nfsd/trace.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> index 4183819ea082..9b32cda54808 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -1370,7 +1370,7 @@ TRACE_EVENT(nfsd_cb_setup,
> TP_fast_assign(
> __entry->cl_boot = clp->cl_clientid.cl_boot;
> __entry->cl_id = clp->cl_clientid.cl_id;
> - strlcpy(__entry->netid, netid, sizeof(__entry->netid));
> + strscpy(__entry->netid, netid, sizeof(__entry->netid));
> __entry->authflavor = authflavor;
> __assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
> clp->cl_cb_conn.cb_addrlen)
>
--
Chuck Lever
Thanks Chuck and Kees for the review.
> > Actually netid should use the __string() and __assign_str()
> > macros rather than open-coding a string copy, I think.
Do you mean something like this?
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 4183819ea082..72a906a053dc 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -1365,19 +1365,19 @@ TRACE_EVENT(nfsd_cb_setup,
__field(u32, cl_id)
__field(unsigned long, authflavor)
__sockaddr(addr, clp->cl_cb_conn.cb_addrlen)
- __array(unsigned char, netid, 8)
+ __string(netid, netid)
),
TP_fast_assign(
__entry->cl_boot = clp->cl_clientid.cl_boot;
__entry->cl_id = clp->cl_clientid.cl_id;
- strlcpy(__entry->netid, netid, sizeof(__entry->netid));
+ __assign_str(netid, netid);
__entry->authflavor = authflavor;
__assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
clp->cl_cb_conn.cb_addrlen)
),
TP_printk("addr=%pISpc client %08x:%08x proto=%s flavor=%s",
__get_sockaddr(addr), __entry->cl_boot, __entry->cl_id,
- __entry->netid, show_nfsd_authflavor(__entry->authflavor))
+ __get_str(netid), show_nfsd_authflavor(__entry->authflavor))
);
> > Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint")
Ack.
> On May 12, 2023, at 7:30 AM, Azeem Shaikh <[email protected]> wrote:
>
> Thanks Chuck and Kees for the review.
>
>>> Actually netid should use the __string() and __assign_str()
>>> macros rather than open-coding a string copy, I think.
>
> Do you mean something like this?
>
> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> index 4183819ea082..72a906a053dc 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -1365,19 +1365,19 @@ TRACE_EVENT(nfsd_cb_setup,
> __field(u32, cl_id)
> __field(unsigned long, authflavor)
> __sockaddr(addr, clp->cl_cb_conn.cb_addrlen)
> - __array(unsigned char, netid, 8)
> + __string(netid, netid)
> ),
> TP_fast_assign(
> __entry->cl_boot = clp->cl_clientid.cl_boot;
> __entry->cl_id = clp->cl_clientid.cl_id;
> - strlcpy(__entry->netid, netid, sizeof(__entry->netid));
> + __assign_str(netid, netid);
> __entry->authflavor = authflavor;
> __assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
> clp->cl_cb_conn.cb_addrlen)
> ),
> TP_printk("addr=%pISpc client %08x:%08x proto=%s flavor=%s",
> __get_sockaddr(addr), __entry->cl_boot, __entry->cl_id,
> - __entry->netid, show_nfsd_authflavor(__entry->authflavor))
> + __get_str(netid), show_nfsd_authflavor(__entry->authflavor))
> );
Yes. I don't remember why I chose to open-code the string
handling in here.
I agree with Kees, also: __assign_str() needs to handle
the memory accesses properly, and I had assumed it did
that already. My bad. That IMO should be handled as a
separate patch.
>>> Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint")
>
> Ack.
I agree that it's not a high priority backport. However,
I expect those who want to use trace points on KASAN-
enabled stable kernels might prefer to have the
__assign_str fix in place, along with this one.
So, I'm good with including Fixes: or leaving it off. Up
to you!
--
Chuck Lever
On Thu, 11 May 2023 09:32:31 -0700
Kees Cook <[email protected]> wrote:
> On Thu, May 11, 2023 at 02:47:54PM +0000, Chuck Lever III wrote:
> > Hello Azeem -
> >
> > > On May 10, 2023, at 3:09 PM, Azeem Shaikh <[email protected]> wrote:
> > >
> > > strlcpy() reads the entire source buffer first.
> > > This read may exceed the destination size limit.
> > > This is both inefficient and can lead to linear read
> > > overflows if a source string is not NUL-terminated [1].
> > > In an effort to remove strlcpy() completely [2], replace
> > > strlcpy() here with strscpy().
> > > No return values were used, so direct replacement is safe.
> >
> > Actually netid should use the __string() and __assign_str()
> > macros rather than open-coding a string copy, I think.
>
> Ah, hm, yeah, this is tracing wrappers.
>
> Steve, is there a reason __assign_str() is using "strcpy" and not
> strscpy()?
Yes. Because __assign_str() predates strscpy() ;-)
Note, to use __assign_str(), you first need to do __string(), which
will do (in all that TRACE_EVENT() macro magic):
#undef __dynamic_array
#define __dynamic_array(type, item, len) \
__item_length = (len) * sizeof(type); \
__data_offsets->item = __data_size + \
offsetof(typeof(*entry), __data); \
__data_offsets->item |= __item_length << 16; \
__data_size += __item_length;
#undef __string
#define __string(item, src) __dynamic_array(char, item, \
strlen((src) ? (const char *)(src) : "(null)") + 1)
In order to save a dynamic size string (or array) it must first
calculate that size with a strlen(). If the source is not terminated,
then this will crash there regardless.
The strlen() is to know how much to allocate on the ring buffer, then a
copy is done to copy it. I guess you could be worried about the size
"changing" between the time it is allocated and copied. If that's the
concern then we could do a length copy.
>
> > Fixes: 3c92fba557c6 ("NFSD: Enhance the nfsd_cb_setup tracepoint")
>
> Yeah, that works. I was on the fence about adding Fixes for these kinds
> of refactoring. Like, it's not really _broken_; we're just trying to
> remove the API.
>
> > > Signed-off-by: Azeem Shaikh <[email protected]>
> > > ---
> > > fs/nfsd/trace.h | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > > index 4183819ea082..9b32cda54808 100644
> > > --- a/fs/nfsd/trace.h
> > > +++ b/fs/nfsd/trace.h
> > > @@ -1370,7 +1370,7 @@ TRACE_EVENT(nfsd_cb_setup,
> > > TP_fast_assign(
> > > __entry->cl_boot = clp->cl_clientid.cl_boot;
> > > __entry->cl_id = clp->cl_clientid.cl_id;
> > > - strlcpy(__entry->netid, netid, sizeof(__entry->netid));
> > > + strscpy(__entry->netid, netid, sizeof(__entry->netid));
> > > __entry->authflavor = authflavor;
> > > __assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
> > > clp->cl_cb_conn.cb_addrlen)
>
> Leaving code context for Steve to see...
>
The above isn't __assign_str(). Not exactly sure what you want me to
see here.
-- Steve