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Mon, 21 Oct 2024 13:45:31 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id OB9CLPtaFmdiRwAAD6G6ig (envelope-from ); Mon, 21 Oct 2024 13:45:31 +0000 Message-ID: <9c0991db-9bf8-414c-b3b0-446023df2a7a@suse.cz> Date: Mon, 21 Oct 2024 15:45:31 +0200 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] mm: add PTE_MARKER_GUARD PTE marker Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Chris Zankel , Max Filippov , Arnd Bergmann , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, Shuah Khan , Christian Brauner , linux-kselftest@vger.kernel.org, Sidhartha Kumar , Jeff Xu , Christoph Hellwig , linux-api@vger.kernel.org, John Hubbard References: <081837b697a98c7fa5832542b20f603d49e0b557.1729440856.git.lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <081837b697a98c7fa5832542b20f603d49e0b557.1729440856.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com,gmx.de]; RCPT_COUNT_TWELVE(0.00)[32]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[google.com,oracle.com,infradead.org,kernel.org,redhat.com,kvack.org,vger.kernel.org,linux.dev,linaro.org,jurassic.park.msu.ru,gmail.com,alpha.franken.de,HansenPartnership.com,gmx.de,zankel.net,arndb.de,chromium.org,nvidia.com]; R_RATELIMIT(0.00)[to_ip_from(RL3py1j7x8bxoj6nr7eaeb97sq)]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:mid,suse.cz:email,oracle.com:email] X-Spam-Flag: NO X-Spam-Level: On 10/20/24 18:20, Lorenzo Stoakes wrote: > Add a new PTE marker that results in any access causing the accessing > process to segfault. Should we distinguish it from other segfaults? Is there a way? I can see memory protection keys use SEGV_PKUERR, but no idea if we have any free values. > This is preferable to PTE_MARKER_POISONED, which results in the same > handling as hardware poisoned memory, and is thus undesirable for cases > where we simply wish to 'soft' poison a range. > > This is in preparation for implementing the ability to specify guard pages > at the page table level, i.e. ranges that, when accessed, should cause > process termination. > > Additionally, rename zap_drop_file_uffd_wp() to zap_drop_markers() - the > function checks the ZAP_FLAG_DROP_MARKER flag so naming it for this single > purpose was simply incorrect. > > We then reuse the same logic to determine whether a zap should clear a > guard entry - this should only be performed on teardown and never on > MADV_DONTNEED or the like. > > Signed-off-by: Lorenzo Stoakes Acked-by: Vlastimil Babka A nit below: > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 906294ac85dc..50e3f6ed73ac 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6353,6 +6353,9 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, > ret = VM_FAULT_HWPOISON_LARGE | > VM_FAULT_SET_HINDEX(hstate_index(h)); > goto out_mutex; > + } else if (marker & PTE_MARKER_GUARD) { > + ret = VM_FAULT_SIGSEGV; > + goto out_mutex; Given we don't support hugetlb, should we WARN_ON_ONCE() if such unexpected marker appears there? > } > } > > diff --git a/mm/memory.c b/mm/memory.c > index 0f614523b9f4..551455cd453f 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1455,7 +1455,7 @@ static inline bool should_zap_folio(struct zap_details *details, > return !folio_test_anon(folio); > } > > -static inline bool zap_drop_file_uffd_wp(struct zap_details *details) > +static inline bool zap_drop_markers(struct zap_details *details) > { > if (!details) > return false; > @@ -1476,7 +1476,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, > if (vma_is_anonymous(vma)) > return; > > - if (zap_drop_file_uffd_wp(details)) > + if (zap_drop_markers(details)) > return; > > for (;;) { > @@ -1671,7 +1671,15 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, > * drop the marker if explicitly requested. > */ > if (!vma_is_anonymous(vma) && > - !zap_drop_file_uffd_wp(details)) > + !zap_drop_markers(details)) > + continue; > + } else if (is_guard_swp_entry(entry)) { > + /* > + * Ordinary zapping should not remove guard PTE > + * markers. Only do so if we should remove PTE markers > + * in general. > + */ > + if (!zap_drop_markers(details)) > continue; > } else if (is_hwpoison_entry(entry) || > is_poisoned_swp_entry(entry)) { > @@ -4003,6 +4011,10 @@ static vm_fault_t handle_pte_marker(struct vm_fault *vmf) > if (marker & PTE_MARKER_POISONED) > return VM_FAULT_HWPOISON; > > + /* Hitting a guard page is always a fatal condition. */ > + if (marker & PTE_MARKER_GUARD) > + return VM_FAULT_SIGSEGV; > + > if (pte_marker_entry_uffd_wp(entry)) > return pte_marker_handle_uffd_wp(vmf); >