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b=k1E2EpB1k5J7CBcJb6cpSck/EYkFoXJ/XOO8TUkLoNokPwku9IASWmksUIjVGuaRH Sij34V1NILT409NuiOjlzlPDCOF6WV5EPJzJoL1kBnHa9F0FmprR92wqyJZDi09Ir7 94eMUFLAmJRdhzNRpiPMevc2+a4sqlCWfkh0ad0B7H1CBFM7wbDYuOqlpb5+ciBe2a AL8VsQs40bUw6r7aiXBtZzfjX7RfbFq/dn4cfFzq/hXbtb9FbFDu5ZI92fvM3n5OMa OfpmLLwptq4WD9EWd9O/znlGB1UnsWh/GDlyLkYy5ehoDsF8692YWhg900C28x+Ya+ YQ4V0+5oJNb5w== Date: Fri, 12 Jun 2026 10:01:41 +0300 From: Mike Rapoport To: Pasha Tatashin Cc: Pratyush Yadav , Tarun Sahu , Andrew Morton , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/memfd_luo: validate serialized_data before conversion Message-ID: References: <2vxzmrx1qjuf.fsf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: EEFAF1C0009 X-Stat-Signature: kdh8owfnsmmopzbgrfk9eyjbf1ifij66 X-HE-Tag: 1781247709-319070 X-HE-Meta: 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 naEHuPW8 CfVeXD+2BQOEnB7Jbn30gNvuPDi1EZAtrNpFmPtdkKmSIPK9uDTLH36hTcXx80yYEMlKXeRvToP8mXRyQGB6ppTYdGCNlH7PsokzS8Vv5+/Zs8/UKpMmGkN0OO7bWqmF3jnOmqKrsZ+1K5d8qoIohwrBc5k99eAXnj/5IsfA/wEAEaqgjKfpkCuCvEbk6MNzVU3A4Ur2Q6xygT8y/l7ho1TPgGCW3C6BNNal7AiVAM4Xm8aq7sclHjEY5ois8jNO4zoavvoXWCek4jyB4if9wbKS46ItdImR+Ae03C2R1OCw+gDHPgIE4WfyZ/H6EM62cI3tx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 11, 2026 at 06:11:13PM +0000, Pasha Tatashin wrote: > On 06-11 17:28, Mike Rapoport wrote: > > On Thu, Jun 11, 2026 at 03:37:12PM +0200, Pratyush Yadav wrote: > > > On Thu, Jun 11 2026, Mike Rapoport wrote: > > > > > > > On Thu, Jun 11, 2026 at 10:30:03AM +0000, Tarun Sahu wrote: > > > >> In memfd_luo_finish() and memfd_luo_retrieve(), phys_to_virt() was called > > > >> on args->serialized_data before checking if the physical address is valid. > > > >> Since physical address 0 does not map to virtual NULL (due to direct > > > >> mapping offsets), the subsequent check 'if (!ser)' was ineffective at > > > >> catching a missing serialized_data, leading to unsafe dereferences later. > > > >> > > > >> Validate that args->serialized_data is non-zero before calling > > > >> phys_to_virt(). > > > >> > > > >> Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd") > > > >> Signed-off-by: Tarun Sahu > > > >> --- > > > >> mm/memfd_luo.c | 10 ++++++---- > > > >> 1 file changed, 6 insertions(+), 4 deletions(-) > > > >> > > > >> diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c > > > >> index 59de210bee5f..10f3983b0060 100644 > > > >> --- a/mm/memfd_luo.c > > > >> +++ b/mm/memfd_luo.c > > > >> @@ -397,10 +397,11 @@ static void memfd_luo_finish(struct liveupdate_file_op_args *args) > > > >> if (args->retrieve_status) > > > >> return; > > > >> > > > >> - ser = phys_to_virt(args->serialized_data); > > > >> - if (!ser) > > > >> + if (!args->serialized_data) > > > > > > > > We really should make args->serialized_data a KHOSER_PTR > > > > > > Hmm, that would also be a good idea. I suppose then it would be a better > > > to directly convert to using KHOSER_PTR() instead of this patch? > > > > Makes sense. > > I think we should systematically cover all phys_to_virt conversions > and add KOSHER_PTR() , instead of an ad-hoc approach of adding it as we > go. So, let's take this patch and do a series where we properly convert > everything and provide guidance for others to use going forward. It's too late for this patch for -rc1. So let's systematically convert all 4 or 5 direct phys_to_virt() conversions in the next cycle and be done with it. We have enough time to make it by -rc2. > Pasha -- Sincerely yours, Mike.