Messages in this thread | | | Subject | Re: [PATCH-next] nbd: fix incomplete validation of ioctl arg | From | Yu Kuai <> | Date | Thu, 20 Apr 2023 20:47:30 +0800 |
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在 2023/02/06 22:58, Zhong Jinghua 写道: > We tested and found an alarm caused by nbd_ioctl arg without verification. > The UBSAN warning calltrace like below: > > UBSAN: Undefined behaviour in fs/buffer.c:1709:35 > signed integer overflow: > -9223372036854775808 - 1 cannot be represented in type 'long long int' > CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1 > Hardware name: linux,dummy-virt (DT) > Call trace: > dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78 > show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158 > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x170/0x1dc lib/dump_stack.c:118 > ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161 > handle_overflow+0x188/0x1dc lib/ubsan.c:192 > __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206 > __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709 > block_write_full_page+0x1f0/0x280 fs/buffer.c:2934 > blkdev_writepage+0x34/0x40 fs/block_dev.c:607 > __writepage+0x68/0xe8 mm/page-writeback.c:2305 > write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240 > generic_writepages+0xdc/0x148 mm/page-writeback.c:2329 > blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114 > do_writepages+0xd4/0x250 mm/page-writeback.c:2344 > > The reason for triggering this warning is __block_write_full_page() > -> i_size_read(inode) - 1 overflow. > inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> bytesize. > We think it is necessary to limit the size of arg to prevent errors. > > Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int. > Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine), > it will become 1 after the coercion, which will return unexpected results. > > Fix it by adding checks to prevent passing in too large numbers.
Looks good to me, feel free to add:
Reviewed-by: Yu Kuai <yukuai3@huawei.com> > > Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com> > --- > drivers/block/nbd.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index 592cfa8b765a..e1c954094b6c 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -325,6 +325,9 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, > if (blk_validate_block_size(blksize)) > return -EINVAL; > > + if (bytesize < 0) > + return -EINVAL; > + > nbd->config->bytesize = bytesize; > nbd->config->blksize_bits = __ffs(blksize); > > @@ -1111,6 +1114,9 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg, > struct nbd_sock *nsock; > int err; > > + /* Arg will be cast to int, check it to avoid overflow */ > + if (arg > INT_MAX) > + return -EINVAL; > sock = nbd_get_socket(nbd, arg, &err); > if (!sock) > return err; >
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