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Howlett" , Alex Sierra , Xianting Tian , Colin Cross , Suren Baghdasaryan , Barry Song , Pasha Tatashin , Suleiman Souhlal , Brian Geffon , Yu Zhao , Tong Tiangen , Liu Shixin , Li kunyu , Anshuman Khandual , Vlastimil Babka , Hugh Dickins , Minchan Kim , Miaohe Lin , Gautam Menghani , Catalin Marinas , Mark Brown , Will Deacon , "Eric W . Biederman" , Thomas Gleixner , Sebastian Andrzej Siewior , Andy Lutomirski , Fenghua Yu , Barret Rhoden , Davidlohr Bueso , "Jason A . Donenfeld" , Dinglan Peng , Pedro Fonseca , Jim Huang , Huichun Feng , Chih-En Lin Subject: [PATCH v3 09/14] mm/mprotect: Break COW PTE before changing protection Date: Tue, 20 Dec 2022 15:27:38 +0800 Message-Id: <20221220072743.3039060-10-shiyn.lin@gmail.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221220072743.3039060-1-shiyn.lin@gmail.com> References: <20221220072743.3039060-1-shiyn.lin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" If the PTE table is COW-ed, break it before changing the protection. Signed-off-by: Chih-En Lin --- mm/mprotect.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/mprotect.c b/mm/mprotect.c index 668bfaa6ed2ae..119116ec8f5e5 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -95,6 +95,9 @@ static unsigned long change_pte_range(struct mmu_gather *= tlb, if (pmd_trans_unstable(pmd)) return 0; =20 + if (break_cow_pte(vma, pmd, addr) < 0) + return 0; + /* * The pmd points to a regular pte so the pmd can't change * from under us even if the mmap_lock is only hold for @@ -305,6 +308,12 @@ static inline int pmd_none_or_clear_bad_unless_trans_h= uge(pmd_t *pmd) return 1; if (pmd_trans_huge(pmdval)) return 0; + /* + * If the entry point to COW-ed PTE, it's write protection bit + * will cause pmd_bad(). + */ + if (!pmd_write(pmdval)) + return 0; if (unlikely(pmd_bad(pmdval))) { pmd_clear_bad(pmd); return 1; --=20 2.37.3