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AJvYcCXJrpmUs4c1C1SW8KtJoP+sByw7fuowxCMBOZmwy9MIVA2OrCaeZK6eq6M5kYrW8IKJC6a1G1z5UKwaRuq7AXswZAd0u10ZkGyhySKF X-Gm-Message-State: AOJu0YygzZzslUTTwr7gDCaypOqaYCAZ8yUG7Y5UhhF5w3KY5xie59gd ifu3PHdng59sD4RsYiQP8yZHtpDO5WgFLAm0miKq387kZvZbP/AJ X-Received: by 2002:a05:6a20:7aaf:b0:1a1:2ff0:4e2f with SMTP id u47-20020a056a207aaf00b001a12ff04e2fmr2553411pzh.60.1709334563529; Fri, 01 Mar 2024 15:09:23 -0800 (PST) Received: from localhost.localdomain ([2407:7000:8942:5500:c1d2:28d4:fa3c:e071]) by smtp.gmail.com with ESMTPSA id c11-20020aa781cb000000b006e4362d0d8csm3487509pfn.36.2024.03.01.15.09.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Mar 2024 15:09:23 -0800 (PST) From: Barry Song <21cnbao@gmail.com> To: viro@zeniv.linux.org.uk, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Cc: herbert@gondor.apana.org.au, Barry Song Subject: [PATCH] iov_iter: call kmap on each page even for lowmem if CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP is enabled Date: Sat, 2 Mar 2024 12:09:08 +1300 Message-Id: <20240301230908.7507-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1792367221897302743 X-GMAIL-MSGID: 1792367221897302743 From: Barry Song copy_page_from_iter_atomic() has the assumption lowmem will only need one kmap to get start page_address() for all pages. This is wrong if the debug option CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP is enabled. This patch fixes it in the same way with skbuff.h by always applying kmap one by one even for lowmem, static inline bool skb_frag_must_loop(struct page *p) { #if defined(CONFIG_HIGHMEM) if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(p)) return true; #endif return false; } Reported-by: Herbert Xu Closes: https://lore.kernel.org/all/ZeGtrvm9WGv5cxQV@gondor.apana.org.au/ Signed-off-by: Barry Song --- -v1: Herbert found and pointed out this problem when he reviewed my patch in crypto/scompress.c; 99.9% of the credit for this patch goes to Herbert. lib/iov_iter.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index e0aa6b440ca5..2e8a5b32f152 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -490,7 +490,7 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset, char *p; n = bytes - copied; - if (PageHighMem(page)) { + if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(page)) { page += offset / PAGE_SIZE; offset %= PAGE_SIZE; n = min_t(size_t, n, PAGE_SIZE - offset); @@ -501,7 +501,8 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset, kunmap_atomic(p); copied += n; offset += n; - } while (PageHighMem(page) && copied != bytes && n > 0); + } while ((IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) || PageHighMem(page)) + && copied != bytes && n > 0); return copied; }