Add __GFP_ZERO flag for alloc_page in function bio_copy_kern to initialize the buffer of a bio. Signed-off-by: Haimin Zhang <tcs.kernel@xxxxxxxxx> --- This can cause a kernel-info-leak problem. 0. This problem occurred in function scsi_ioctl. If the parameter cmd is SCSI_IOCTL_SEND_COMMAND, the function scsi_ioctl will call sg_scsi_ioctl to further process. 1. In function sg_scsi_ioctl, it creates a scsi request and calls blk_rq_map_kern to map kernel data to a request. 3. blq_rq_map_kern calls bio_copy_kern to request a bio. 4. bio_copy_kern calls alloc_page to request the buffer of a bio. In the case of reading, it wouldn't fill anything into the buffer. ``` __alloc_pages+0xbbf/0x1090 build/../mm/page_alloc.c:5409 alloc_pages+0x8a5/0xb80 bio_copy_kern build/../block/blk-map.c:449 [inline] blk_rq_map_kern+0x813/0x1400 build/../block/blk-map.c:640 sg_scsi_ioctl build/../drivers/scsi/scsi_ioctl.c:618 [inline] scsi_ioctl+0x40c0/0x4600 build/../drivers/scsi/scsi_ioctl.c:932 sg_ioctl_common build/../drivers/scsi/sg.c:1112 [inline] sg_ioctl+0x3351/0x4c10 build/../drivers/scsi/sg.c:1165 vfs_ioctl build/../fs/ioctl.c:51 [inline] __do_sys_ioctl build/../fs/ioctl.c:874 [inline] __se_sys_ioctl+0x2df/0x4a0 build/../fs/ioctl.c:860 __x64_sys_ioctl+0xd8/0x110 build/../fs/ioctl.c:860 do_syscall_x64 build/../arch/x86/entry/common.c:51 [inline] do_syscall_64+0x54/0xd0 build/../arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x44/0xae ``` 5. Then this request will be sent to the disk driver. When bio is finished, bio_copy_kern_endio_read will copy the readed content back to parameter data from the bio. But if the block driver didn't process this request, the buffer of bio is still unitialized. ``` memcpy_from_page build/../include/linux/highmem.h:346 [inline] memcpy_from_bvec build/../include/linux/bvec.h:207 [inline] bio_copy_kern_endio_read+0x4a3/0x620 build/../block/blk-map.c:403 bio_endio+0xa7f/0xac0 build/../block/bio.c:1491 req_bio_endio build/../block/blk-mq.c:674 [inline] blk_update_request+0x1129/0x22d0 build/../block/blk-mq.c:742 scsi_end_request+0x119/0xe40 build/../drivers/scsi/scsi_lib.c:543 scsi_io_completion+0x329/0x810 build/../drivers/scsi/scsi_lib.c:939 scsi_finish_command+0x6e3/0x700 build/../drivers/scsi/scsi.c:199 scsi_complete+0x239/0x640 build/../drivers/scsi/scsi_lib.c:1441 blk_complete_reqs build/../block/blk-mq.c:892 [inline] blk_done_softirq+0x189/0x260 build/../block/blk-mq.c:897 __do_softirq+0x1ee/0x7c5 build/../kernel/softirq.c:558 ``` 6. Finally, the internal buffer's content is copied to the user buffer which is specified by the parameter sic->data of sg_scsi_ioctl. _copy_to_user+0x1c9/0x270 build/../lib/usercopy.c:33 copy_to_user build/../include/linux/uaccess.h:209 [inline] sg_scsi_ioctl build/../drivers/scsi/scsi_ioctl.c:634 [inline] scsi_ioctl+0x44d9/0x4600 build/../drivers/scsi/scsi_ioctl.c:932 sg_ioctl_common build/../drivers/scsi/sg.c:1112 [inline] sg_ioctl+0x3351/0x4c10 build/../drivers/scsi/sg.c:1165 vfs_ioctl build/../fs/ioctl.c:51 [inline] __do_sys_ioctl build/../fs/ioctl.c:874 [inline] __se_sys_ioctl+0x2df/0x4a0 build/../fs/ioctl.c:860 __x64_sys_ioctl+0xd8/0x110 build/../fs/ioctl.c:860 do_syscall_x64 build/../arch/x86/entry/common.c:51 [inline] do_syscall_64+0x54/0xd0 build/../arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x44/0xae block/blk-map.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-map.c b/block/blk-map.c index 4526adde0156..c7f71d83eff1 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -446,7 +446,7 @@ static struct bio *bio_copy_kern(struct request_queue *q, void *data, if (bytes > len) bytes = len; - page = alloc_page(GFP_NOIO | gfp_mask); + page = alloc_page(GFP_NOIO | __GFP_ZERO | gfp_mask); if (!page) goto cleanup; -- 2.30.1 (Apple Git-130)
