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Wed, 27 May 2026 15:26:09 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: ARr5XTyvjWRZ Date: Wed, 27 May 2026 15:25:39 -0400 From: "Chuck Lever" To: "Jeff Layton" , "Chuck Lever" , NeilBrown , "Olga Kornievskaia" , "Dai Ngo" , "Tom Talpey" , "Sasha Levin" Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: <20260527-pnfs-fixes-v1-1-784f39dc1eca@kernel.org> References: <20260527-pnfs-fixes-v1-1-784f39dc1eca@kernel.org> Subject: Re: [PATCH] nfsd: fix XDR padding calculation in ff_encode_getdeviceinfo Content-Type: text/plain Content-Transfer-Encoding: 7bit On Wed, May 27, 2026, at 2:30 PM, Jeff Layton wrote: > nfsd4_ff_encode_getdeviceinfo() computes the da_addr_body reservation > as 16 + netid_len + addr_len, but the subsequent xdr_encode_opaque() > calls emit 8 + round_up(netid_len, 4) + round_up(addr_len, 4) bytes. > The mismatch means the declared da_addr_body length exceeds the actual > encoded data by 2-8 bytes on every flexfile GETDEVICEINFO reply, > leaking stale reply-page content to the client and mis-aligning the > subsequent version list decode. > > Use xdr_align_size() for each string length to match what > xdr_encode_opaque() actually writes. > > Fixes: efcae97fa425 ("NFSD: da_addr_body field missing in some > GETDEVICEINFO replies") > Assisted-by: kres:claude-opus-4-6 > Signed-off-by: Jeff Layton > --- > fs/nfsd/flexfilelayoutxdr.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/nfsd/flexfilelayoutxdr.c b/fs/nfsd/flexfilelayoutxdr.c > index f9f7e38cba13..7f357dbd1bb1 100644 > --- a/fs/nfsd/flexfilelayoutxdr.c > +++ b/fs/nfsd/flexfilelayoutxdr.c > @@ -94,7 +94,8 @@ nfsd4_ff_encode_getdeviceinfo(struct xdr_stream *xdr, > } > > /* len + padding for two strings */ > - addr_len = 16 + da->netaddr.netid_len + da->netaddr.addr_len; > + addr_len = 8 + xdr_align_size(da->netaddr.netid_len) + > + xdr_align_size(da->netaddr.addr_len); > ver_len = 20; > > len = 4 + ver_len + 4 + addr_len; > > --- > base-commit: b69fc3eaa867d0caa904634ea7a1b4569411b163 > change-id: 20260527-pnfs-fixes-23451bb03d57 > > Best regards, > -- > Jeff Layton Fixes tag might/should be 9b9960a0ca47 ? LLM reviews vary on this. nfsd4_ff_encode_layoutget at fs/nfsd/flexfilelayoutxdr.c:40-41 has the same unaligned pattern for UID/GID strings: 8 + uid.len + 8 + gid.len. Do you intend to address that calculation as well? My preference here is to convert to xdrgen instead, but that's a much bigger and less back-portable change. -- Chuck Lever