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[2a02:3100:a979:9501:3df6:d7fa:8a5a:6c5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48588394fa1sm1005070f8f.8.2026.09.03.13.37.31 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 03 Sep 2026 13:37:32 -0700 (PDT) From: Karl Mehltretter To: Vlastimil Babka , Harry Yoo , Andrew Morton Cc: Karl Mehltretter , Rasmus Villemoes , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Catalin Marinas , Kees Cook , "Gustavo A . R . Silva" , Arnd Bergmann , Greg Kroah-Hartman , Shuah Khan , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH v3 3/5] slab: handle ERR_PTR values in kfree and hardened usercopy Date: Thu, 3 Sep 2026 22:37:18 +0200 Message-Id: <20260903203720.63689-4-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260903203720.63689-1-kmehltretter@gmail.com> References: <20260903203720.63689-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Passing an ERR_PTR to kfree() currently reaches virt_to_page() and may fault. Warn and return instead, leaving the bad caller visible without using the pointer as allocator metadata. Also reject ERR_PTR values in hardened usercopy. Keep both checks separate from ZERO_OR_NULL_PTR(), whose exact matching is required by krealloc(). Link: https://lore.kernel.org/r/CAG48ez05QVn6_gQ2TBrRa1a_DWQoaSSYubUsu5YMWxx-gqMijQ@mail.gmail.com Link: https://lore.kernel.org/r/202608111716.0FA9DB17@keescook Link: https://github.com/KSPP/linux/issues/93 Assisted-by: LLM Signed-off-by: Karl Mehltretter --- mm/slub.c | 3 +++ mm/usercopy.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/mm/slub.c b/mm/slub.c index f9b56cb439e7..027b44dd7f07 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6780,6 +6780,9 @@ void kfree(const void *object) if (unlikely(ZERO_OR_NULL_PTR(object))) return; + if (WARN_ON(IS_ERR(object))) + return; + page = virt_to_page(object); slab = page_slab(page); if (!slab) { diff --git a/mm/usercopy.c b/mm/usercopy.c index 5de7a518b1b1..c8d8703544c6 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -157,6 +157,9 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, /* Reject if NULL or ZERO-allocation. */ if (ZERO_OR_NULL_PTR(ptr)) usercopy_abort("null address", NULL, to_user, ptr, n); + + if (IS_ERR_VALUE(ptr)) + usercopy_abort("ERR_PTR", NULL, to_user, ptr, n); } static inline void check_heap_object(const void *ptr, unsigned long n, -- 2.53.0