| Message ID | 20230510220952.3507366-1-azeemshaikh38@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | NFSD: Replace all non-returning strlcpy with strscpy | expand |
Hello Azeem - > On May 10, 2023, at 3:09 PM, Azeem Shaikh <azeemshaikh38@gmail.com> 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 <azeemshaikh38@gmail.com> > --- > 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
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 <azeemshaikh38@gmail.com> 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()? > 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 <azeemshaikh38@gmail.com> > > --- > > 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...
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 <azeemshaikh38@gmail.com> 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 Fri, May 12, 2023 at 10:38 AM Chuck Lever III <chuck.lever@oracle.com> wrote: > > > > > On May 12, 2023, at 7:30 AM, Azeem Shaikh <azeemshaikh38@gmail.com> 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. Thanks I'll send out a patch with the __assign_str replacement for now. I'll wait for Kees and Steve to respond on how to fix the memory access in __assign_str. > >>> 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! > Will include it :)
On Thu, 11 May 2023 09:32:31 -0700 Kees Cook <keescook@chromium.org> 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 <azeemshaikh38@gmail.com> 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 <azeemshaikh38@gmail.com> > > > --- > > > 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
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)
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 <azeemshaikh38@gmail.com> --- fs/nfsd/trace.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)