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Fri, 08 Nov 2019 05:02:28 -0800 (PST) Received: from binjiang-hz-dhcp091254.china.nsn-net.net ([131.228.2.20]) by smtp.gmail.com with ESMTPSA id b8sm5873976wrt.39.2019.11.08.05.02.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Nov 2019 05:02:27 -0800 (PST) From: Li Xinhai To: linux-mm@kvack.org Cc: Andrew Morton , Naoya Horiguchi , Michal Hocko , Vlastimil Babka , Hugh Dickins , linux-man Subject: [PATCH v4 2/2] mm: Fix checking unmapped holes for mbind Date: Fri, 8 Nov 2019 21:01:44 +0800 Message-Id: <1573218104-11021-3-git-send-email-lixinhai.lxh@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1573218104-11021-1-git-send-email-lixinhai.lxh@gmail.com> References: <1573218104-11021-1-git-send-email-lixinhai.lxh@gmail.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: mbind() is required to report EFAULT if range, specified by addr and len, contains unmapped holes. In current implementation, below rules are applied for this checking: 1 Unmapped holes at any part of the specified range should be reported as EFAULT if mbind() for none MPOL_DEFAULT cases; 2 Unmapped holes at any part of the specified range should be ignored (do not reprot EFAULT) if mbind() for MPOL_DEFAULT case; 3 The whole range in an unmapped hole should be reported as EFAULT; Note that rule 2 does not fullfill the mbind() API definition, but since that behavior has existed for long days (the internal flag MPOL_MF_DISCONTIG_OK is for this purpose), this patch does not plan to change it. In current code, application observed inconsistent behavior on rule 1 and rule 2 respectively. That inconsistency is fixed as below details. Cases of rule 1: 1) Hole at head side of range. Current code reprot EFAULT, no change by this patch. [ vma ][ hole ][ vma ] [ range ] 2) Hole at middle of range. Current code report EFAULT, no change by this patch. [ vma ][ hole ][ vma ] [ range ] 3) Hole at tail side of range. Current code do not report EFAULT, this patch fix it. [ vma ][ hole ][ vma ] [ range ] Cases of rule 2: 1) Hole at head side of range. Current code reprot EFAULT, this patch fix it. [ vma ][ hole ][ vma ] [ range ] 2) Hole at middle of range. Current code do not report EFAULT, no change by this patch. this patch. [ vma ][ hole ][ vma] [ range ] 3) Hole at tail side of range. Current code do not report EFAULT, no change by this patch. [ vma ][ hole ][ vma] [ range ] This patch has no changes to rule 3. The unmapped hole checking can also be handled by using .pte_hole(), instead of .test_walk(). But .pte_hole() is called for holes inside and outside vma, which causes more cost, so this patch keeps the original design with .test_walk(). Fixes: 6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()") Cc: Andrew Morton Cc: Naoya Horiguchi Cc: Michal Hocko Cc: Vlastimil Babka Cc: Hugh Dickins Cc: linux-man Signed-off-by: Li Xinhai --- mm/mempolicy.c | 40 +++++++++++++++++++++++++++------------- 1 file changed, 27 insertions(+), 13 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 807f06f..c697b29 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -410,7 +410,9 @@ struct queue_pages { struct list_head *pagelist; unsigned long flags; nodemask_t *nmask; - struct vm_area_struct *prev; + unsigned long start; + unsigned long end; + struct vm_area_struct *first; }; /* @@ -619,14 +621,20 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, unsigned long flags = qp->flags; /* range check first */ - if (!(flags & MPOL_MF_DISCONTIG_OK)) { - if (!vma->vm_next && vma->vm_end < end) - return -EFAULT; - if (qp->prev && qp->prev->vm_end < vma->vm_start) + VM_BUG_ON((vma->vm_start > start) || (vma->vm_end < end)); + + if (!qp->first) { + qp->first = vma; + if (!(flags & MPOL_MF_DISCONTIG_OK) && + (qp->start < vma->vm_start)) + /* hole at head side of range */ return -EFAULT; } - - qp->prev = vma; + if (!(flags & MPOL_MF_DISCONTIG_OK) && + ((vma->vm_end < qp->end) && + (!vma->vm_next || vma->vm_end < vma->vm_next->vm_start))) + /* hole at middle or tail of range */ + return -EFAULT; /* * Need check MPOL_MF_STRICT to return -EIO if possible @@ -638,8 +646,6 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, if (endvma > end) endvma = end; - if (vma->vm_start > start) - start = vma->vm_start; if (flags & MPOL_MF_LAZY) { /* Similar to task_numa_work, skip inaccessible VMAs */ @@ -680,14 +686,23 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, nodemask_t *nodes, unsigned long flags, struct list_head *pagelist) { + int err; struct queue_pages qp = { .pagelist = pagelist, .flags = flags, .nmask = nodes, - .prev = NULL, + .start = start, + .end = end, + .first = NULL, }; - return walk_page_range(mm, start, end, &queue_pages_walk_ops, &qp); + err = walk_page_range(mm, start, end, &queue_pages_walk_ops, &qp); + + if (!qp.first) + /* whole range in hole */ + err = -EFAULT; + + return err; } /* @@ -739,8 +754,7 @@ static int mbind_range(struct mm_struct *mm, unsigned long start, unsigned long vmend; vma = find_vma(mm, start); - if (!vma || vma->vm_start > start) - return -EFAULT; + VM_BUG_ON(!vma); prev = vma->vm_prev; if (start > vma->vm_start)