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Mon, 16 Jan 2023 05:08:36 -0800 (PST) Date: Mon, 16 Jan 2023 16:08:33 +0300 From: Dan Carpenter To: Baoquan He Cc: oe-kbuild@lists.linux.dev, linux-mm@kvack.org, lkp@intel.com, oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org, urezki@gmail.com, lstoakes@gmail.com, stephen.s.brennan@oracle.com, willy@infradead.org, akpm@linux-foundation.org, hch@infradead.org Subject: Re: [PATCH v3 3/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas Message-ID: References: <20230113031921.64716-4-bhe@redhat.com> <202301132345.KVjvHMFq-lkp@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 6776540018 X-Rspamd-Server: rspam01 X-Stat-Signature: r8t17dw3ke3gqe7xjkfxj1kuzghatejf X-HE-Tag: 1673874518-466893 X-HE-Meta: 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 ii8y4ltF T9IYNxJqIaFiT7L+7iTwhJyfsj1lNB+lMcNo4gcalEfSmnQn9cTyyWIqKewLqDNEw24/7XP41CeTwVJoBLl/W6IjyscUL0AW1dDKyiZHaMjfhC43GhZEMWJYHy8EuRqXu2K6IGySbPOrOZFg= 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: On Sun, Jan 15, 2023 at 10:08:55PM +0800, Baoquan He wrote: > > f181234a5a21fd0 Chen Wandun 2021-09-02 3650 if ((unsigned long)addr + count <= va->va_start) > > f181234a5a21fd0 Chen Wandun 2021-09-02 3651 goto finished; > > f181234a5a21fd0 Chen Wandun 2021-09-02 3652 > > f608788cd2d6cae Serapheim Dimitropoulos 2021-04-29 3653 list_for_each_entry_from(va, &vmap_area_list, list) { > > e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3654 if (!count) > > e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3655 break; > > e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3656 > > 129dbdf298d7383 Baoquan He 2023-01-13 3657 vm = va->vm; > > 129dbdf298d7383 Baoquan He 2023-01-13 3658 flags = va->flags & VMAP_FLAGS_MASK; > > 129dbdf298d7383 Baoquan He 2023-01-13 3659 > > 129dbdf298d7383 Baoquan He 2023-01-13 3660 if (!vm && !flags) > > ^^^ > > vm can be NULL if a flag in VMAP_FLAGS_MASK is set. > > > > e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3661 continue; > > Right, after the 'continue;' line, only two cases could happen when it > comes here. (vm != null) or (vm->flags & VMAP_RAM) is true. > You're saying VMAP_RAM, but strictly speaking the code is checking VMAP_FLAGS_MASK and not VMAP_RAM. +#define VMAP_RAM 0x1 /* indicates vm_map_ram area*/ +#define VMAP_BLOCK 0x2 /* mark out the vmap_block sub-type*/ +#define VMAP_FLAGS_MASK 0x3 If we assume that vm is NULL, VMAP_BLOCK is set and VMAP_RAM is clear then it would lead to a NULL dereference. There might be reasons why that combination is impossible outside the function but we can't tell from the information we have here. Which is fine, outside information is a common reason for false positives with this check. But I was just concerned about the mix of VMAP_FLAGS_MASK and VMAP_RAM. regards, dan carpenter > > e81ce85f960c2e2 Joonsoo Kim 2013-04-29 3662 > > 129dbdf298d7383 Baoquan He 2023-01-13 3663 vaddr = (char *) va->va_start; > > 129dbdf298d7383 Baoquan He 2023-01-13 @3664 size = vm ? get_vm_area_size(vm) : va_size(va); > > ^^ > > > > 129dbdf298d7383 Baoquan He 2023-01-13 3665 > > 129dbdf298d7383 Baoquan He 2023-01-13 3666 if (addr >= vaddr + size) > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3667 continue; > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3668 while (addr < vaddr) { > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3669 if (count == 0) > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3670 goto finished; > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3671 *buf = '\0'; > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3672 buf++; > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3673 addr++; > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3674 count--; > > ^1da177e4c3f415 Linus Torvalds 2005-04-16 3675 } > > 129dbdf298d7383 Baoquan He 2023-01-13 3676 n = vaddr + size - addr; > > d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3677 if (n > count) > > d0107eb07320b5d KAMEZAWA Hiroyuki 2009-09-21 3678 n = count; > > 129dbdf298d7383 Baoquan He 2023-01-13 3679 > > 129dbdf298d7383 Baoquan He 2023-01-13 3680 if (flags & VMAP_RAM) > > > > assume VMAP_RAM is not set > > OK, then vm is not null. > > > > 129dbdf298d7383 Baoquan He 2023-01-13 3681 vmap_ram_vread(buf, addr, n, flags); > > 129dbdf298d7383 Baoquan He 2023-01-13 @3682 else if (!(vm->flags & VM_IOREMAP)) > > ^^^^^^^^^ > > Unchecked dereference. Should this be "flags" instead of "vm->flags"? > > Thus, here, in 'else if', vm is not null. And in this 'else if', we are > intending to check vm->flags. I don't see issue or risk here. Please > help check if I miss anything. > > Thanks > Baoquan >