Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:[EOL][EOL]nbd: fix incomplete validation of ioctl arg[EOL][EOL]We tested and found an alarm caused by nbd_ioctl arg without verification.[EOL]The UBSAN warning calltrace like below:[EOL][EOL]UBSAN: Undefined behaviour in fs/buffer.c:1709:35[EOL]signed integer overflow:[EOL]-9223372036854775808 - 1 cannot be represented in type 'long long int'[EOL]CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1[EOL]Hardware name: linux,dummy-virt (DT)[EOL]Call trace:[EOL] dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78[EOL] show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158[EOL] __dump_stack lib/dump_stack.c:77 [inline][EOL] dump_stack+0x170/0x1dc lib/dump_stack.c:118[EOL] ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161[EOL] handle_overflow+0x188/0x1dc lib/ubsan.c:192[EOL] __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206[EOL] __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709[EOL] block_write_full_page+0x1f0/0x280 fs/buffer.c:2934[EOL] blkdev_writepage+0x34/0x40 fs/block_dev.c:607[EOL] __writepage+0x68/0xe8 mm/page-writeback.c:2305[EOL] write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240[EOL] generic_writepages+0xdc/0x148 mm/page-writeback.c:2329[EOL] blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114[EOL] do_writepages+0xd4/0x250 mm/page-writeback.c:2344[EOL][EOL]The reason for triggering this warning is __block_write_full_page()[EOL]-> i_size_read(inode) - 1 overflow.[EOL]inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> bytesize.[EOL]We think it is necessary to limit the size of arg to prevent errors.[EOL][EOL]Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int.[EOL]Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine),[EOL]it will become 1 after the coercion, which will return unexpected results.[EOL][EOL]Fix it by adding checks to prevent passing in too large numbers.