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Fri, 1 May 2026 08:44:21 -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 Date: Fri, 01 May 2026 08:44:01 -0400 From: "Chuck Lever" To: "Jeff Layton" , "Misbah Anjum N" , "Linux Kernel" , "Linux Nfs" Cc: "Linuxppc Dev" , "Chuck Lever" , venkat88@linux.ibm.com, "Linux Next" Message-Id: <8e8847fb-0eff-46b0-97dc-fe683c706db3@app.fastmail.com> In-Reply-To: References: <8cf80f450085ac17164e8fa1391e9635@linux.ibm.com> Subject: Re: [BUG] [powerpc] [next-20260216/17] nfsd: use-after-free in cache_check_rcu() triggered by sosreport on ppc64le Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Fri, May 1, 2026, at 3:06 AM, Jeff Layton wrote: > On Fri, 2026-05-01 at 02:15 +0530, Misbah Anjum N wrote: >> Hi, >>=20 >> Following up on my bug report, I have completed a git bisect and have=20 >> critical new findings to report. >> Ref:=20 >> https://lore.kernel.org/linux-next/dcd371d3a95815a84ba7de52cef447b8@l= inux.ibm.com/T/#u >>=20 >> Current Status: Bug Has Propagated from linux-next to Mainline. >> First Bad commit identified: da6b5aae84beb0917ecb0c9fbc71169d145397ff >>=20 >> The use-after-free bug in cache_check_rcu() that I originally reporte= d=20 >> in linux-next (6.19.0-next-20260216/17) has now propagated into mainl= ine=20 >> and is confirmed present in: >> - mainline (Tested on Latest kernel as of 2026-04-30 - commit=20 >> 08d0d3466664) >> - linux-next (Tested on Latest kernel as of 2026-04-30) >>=20 >> This bug is causing failures on ppc64le systems: >> 1. Kernel panics: 100% reproducible crashes when sosreport runs >> 2. CI/Testing failures: All automated Avocado-vt KVM testing on ppc64= le=20 >> is failing >> 3. Use-after-free corruption: Memory corruption with corrupted pointe= rs=20 >> containing >> ASCII strings ("libz.so.", "export_cap") or poison patterns=20 >> (0xcccccccccccccccc) >>=20 > > Thanks for the bug report. I must have missed your earlier email. You didn=E2=80=99t miss it. We responded to that report in February with a fix that you and Neil both reviewed and it is in v7.0 now. That fix addressed one instance of this problem; there are actually several more, all in the same UAF class. I have a patch series nearly complete to address these issues. The issue Misbah reports here is not the same as the February issue, though it is very similar. > The commit you landed on is a merge commit and is not likely to be the > cause, particularly since that merge was for x86 drivers and you're > seeing this on PPC. Is this reproducible on other architectures? We have an internal bug reporting the same stack trace on ARM64. Now that we have both a reproducer and a platform that is easily accessible it will be straightforward to confirm these issues are fully addressed before we merge the new fixes. --=20 Chuck Lever