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Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Simon Horman" Cc: linux-nfs@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: <20261022-integ-page-reuse-v1-1-fbe571857d4f@gmail.com> References: <20261022-integ-page-reuse-v1-1-fbe571857d4f@gmail.com> Subject: Re: [PATCH] SUNRPC: avoid possible page reuse from svcauth_gss_wrap_integ() Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Oct 22, 2026, at 9:10 AM, Michael Lowman via B4 Relay wrote: > From: Michael Lowman > > Commit 7702378ac4d4 ("SUNRPC: Convert svcauth_gss_wrap_integ() to > use xdr_stream()") and its parent changed from calculating the > integrity checksum in-place in an unused part of the response buffer > to calculating in a scratch buffer and appending it to the response > stream. While the unused part of the response buffer happened to > always end on the first page, the append always occurs on the last. > > If less than 32 bytes remain before the page boundary, some or all > of the checksum will be written to the next page. But since the xdr > functions do not update the response's page accounting, the page > will be immediately available for reuse. Data from another request > will overwrite the portion of the checksum on the new page. > > Avoid this by marking the page as used when needed. > > Signed-off-by: Michael Lowman > Fixes: 7702378ac4d4 ("SUNRPC: Convert svcauth_gss_wrap_integ() to use > xdr_stream()") Commit d1eafc3bab9f "SUNRPC: in svcauth_gss_wrap_integ() resync rq_next_page after the GSS wrap", now in the nfsd-testing branch, already addresses this issue. Thanks for confirming the finding! -- Chuck Lever (Come to NFS bake-a-thon! https://nfsv4bat.org)