scsi: use-after-free in bio_copy_from_iter

[Dmitry Vyukov]

Hello,

The following program triggers use-after-free in bio_copy_from_iter:
https://gist.githubusercontent.com/dvyukov/80cd94b4e4c288f16ee4c787d404118b/raw/10536069562444da51b758bb39655b514ff93b45/gistfile1.txt


==================================================================
BUG: KASAN: use-after-free in copy_from_iter+0xf30/0x15e0 at addr
ffff880062c6e02a
Read of size 4096 by task a.out/8529
page:ffffea00018b1b80 count:2 mapcount:0 mapping:ffff88006c80e9d0 index:0x1695
flags: 0x5fffc0000000864(referenced|lru|active|private)
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88003ebcea00
CPU: 1 PID: 8529 Comm: a.out Not tainted 4.9.0-rc6+ #55
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff880039ca6770 ffffffff834c3bb9 ffffffff00000001 1ffff10007394c81
 ffffed0007394c79 0000000041b58ab3 ffffffff89575c30 ffffffff834c38cb
 0000000000000000 0000000000000000 0000000000000001 0000000000000000
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff834c3bb9>] dump_stack+0x2ee/0x3f5 lib/dump_stack.c:51
 [<     inline     >] print_address_description mm/kasan/report.c:211
 [<     inline     >] kasan_report_error mm/kasan/report.c:285
 [<ffffffff819f18b8>] kasan_report+0x418/0x440 mm/kasan/report.c:305
 [<     inline     >] check_memory_region_inline mm/kasan/kasan.c:308
 [<ffffffff819f0509>] check_memory_region+0x139/0x190 mm/kasan/kasan.c:315
 [<ffffffff819f0a43>] memcpy+0x23/0x50 mm/kasan/kasan.c:350
 [<ffffffff83525d10>] copy_from_iter+0xf30/0x15e0 lib/iov_iter.c:559
 [<ffffffff83526834>] copy_page_from_iter+0x474/0x860 lib/iov_iter.c:614
 [<     inline     >] bio_copy_from_iter block/bio.c:1025
 [<ffffffff833dfc10>] bio_copy_user_iov+0xb50/0xf10 block/bio.c:1226
 [<     inline     >] __blk_rq_map_user_iov block/blk-map.c:56
 [<ffffffff83421c15>] blk_rq_map_user_iov+0x295/0x930 block/blk-map.c:130
 [<ffffffff834223e9>] blk_rq_map_user+0x139/0x1e0 block/blk-map.c:159
 [<     inline     >] sg_start_req drivers/scsi/sg.c:1757
 [<ffffffff8470269a>] sg_common_write.isra.20+0x12da/0x1b20
drivers/scsi/sg.c:772
 [<ffffffff8470774a>] sg_write+0x78a/0xda0 drivers/scsi/sg.c:675
 [<ffffffff81a6fabe>] __vfs_write+0x65e/0x830 fs/read_write.c:510
 [<ffffffff81a6fd7c>] __kernel_write+0xec/0x340 fs/read_write.c:532
 [<ffffffff81b41e7c>] write_pipe_buf+0x19c/0x260 fs/splice.c:814
 [<     inline     >] splice_from_pipe_feed fs/splice.c:519
 [<ffffffff81b426af>] __splice_from_pipe+0x31f/0x750 fs/splice.c:643
 [<ffffffff81b45dcc>] splice_from_pipe+0x1dc/0x300 fs/splice.c:678
 [<ffffffff81b45f95>] default_file_splice_write+0x45/0x90 fs/splice.c:826
 [<     inline     >] do_splice_from fs/splice.c:868
 [<ffffffff81b3e2ba>] direct_splice_actor+0x12a/0x190 fs/splice.c:1035
 [<ffffffff81b40706>] splice_direct_to_actor+0x2c6/0x840 fs/splice.c:990
 [<ffffffff81b40f4e>] do_splice_direct+0x2ce/0x470 fs/splice.c:1078
 [<ffffffff81a7459f>] do_sendfile+0x73f/0x1060 fs/read_write.c:1401
 [<     inline     >] SYSC_sendfile64 fs/read_write.c:1456
 [<ffffffff81a7677e>] SyS_sendfile64+0xee/0x1a0 fs/read_write.c:1448
 [<ffffffff8814cf85>] entry_SYSCALL_64_fastpath+0x23/0xc6
arch/x86/entry/entry_64.S:209
Memory state around the buggy address:
 ffff880062c6ef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff880062c6ef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff880062c6f000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff880062c6f080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff880062c6f100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
Disabling lock debugging due to kernel taint
BUG: unable to handle kernel paging request at ffff880062c6f000
IP: [<ffffffff835051c2>] __memcpy+0x12/0x20 arch/x86/lib/memcpy_64.S:37
PGD c53d067 [  494.351750] PUD c540067
PMD 7fdea067 [  494.351750] PTE 8000000062c6f060

Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
Modules linked in:
CPU: 1 PID: 8529 Comm: a.out Tainted: G    B           4.9.0-rc6+ #55
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88003c54e3c0 task.stack: ffff880039ca0000
RIP: 0010:[<ffffffff835051c2>]  [<ffffffff835051c2>]
__memcpy+0x12/0x20 arch/x86/lib/memcpy_64.S:37
RSP: 0018:ffff880039ca6838  EFLAGS: 00010246
RAX: ffff880031b99000 RBX: 0000000000001000 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffff880062c6effa RDI: ffff880031b99fd0
RBP: ffff880039ca6858 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000200 R11: ffffed00063733ff R12: ffff880031b99000
R13: ffff880062c6e02a R14: ffff880039ca6f70 R15: ffff880039ca6d18
FS:  00007f7a78013700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff880062c6f000 CR3: 000000006411f000 CR4: 00000000000006e0
Stack:
 ffffffff819f0a65 ffff880039ca71a0 0000000000001000 0000000000002000
 ffff880039ca6d40 ffffffff83525d10 0000000041b58ab3 ffffffff89576240
 ffffffff00000001 0000000000000000 0000000041b58ab3 ffffffff894d07b0
Call Trace:
 [<ffffffff83525d10>] copy_from_iter+0xf30/0x15e0 lib/iov_iter.c:559
 [<ffffffff83526834>] copy_page_from_iter+0x474/0x860 lib/iov_iter.c:614
 [<     inline     >] bio_copy_from_iter block/bio.c:1025
 [<ffffffff833dfc10>] bio_copy_user_iov+0xb50/0xf10 block/bio.c:1226
 [<     inline     >] __blk_rq_map_user_iov block/blk-map.c:56
 [<ffffffff83421c15>] blk_rq_map_user_iov+0x295/0x930 block/blk-map.c:130
 [<ffffffff834223e9>] blk_rq_map_user+0x139/0x1e0 block/blk-map.c:159
 [<     inline     >] sg_start_req drivers/scsi/sg.c:1757
 [<ffffffff8470269a>] sg_common_write.isra.20+0x12da/0x1b20
drivers/scsi/sg.c:772
 [<ffffffff8470774a>] sg_write+0x78a/0xda0 drivers/scsi/sg.c:675
 [<ffffffff81a6fabe>] __vfs_write+0x65e/0x830 fs/read_write.c:510
 [<ffffffff81a6fd7c>] __kernel_write+0xec/0x340 fs/read_write.c:532
 [<ffffffff81b41e7c>] write_pipe_buf+0x19c/0x260 fs/splice.c:814
 [<     inline     >] splice_from_pipe_feed fs/splice.c:519
 [<ffffffff81b426af>] __splice_from_pipe+0x31f/0x750 fs/splice.c:643
 [<ffffffff81b45dcc>] splice_from_pipe+0x1dc/0x300 fs/splice.c:678
 [<ffffffff81b45f95>] default_file_splice_write+0x45/0x90 fs/splice.c:826
 [<     inline     >] do_splice_from fs/splice.c:868
 [<ffffffff81b3e2ba>] direct_splice_actor+0x12a/0x190 fs/splice.c:1035
 [<ffffffff81b40706>] splice_direct_to_actor+0x2c6/0x840 fs/splice.c:990
 [<ffffffff81b40f4e>] do_splice_direct+0x2ce/0x470 fs/splice.c:1078
 [<ffffffff81a7459f>] do_sendfile+0x73f/0x1060 fs/read_write.c:1401
 [<     inline     >] SYSC_sendfile64 fs/read_write.c:1456
 [<ffffffff81a7677e>] SyS_sendfile64+0xee/0x1a0 fs/read_write.c:1448
 [<ffffffff8814cf85>] entry_SYSCALL_64_fastpath+0x23/0xc6
arch/x86/entry/entry_64.S:209
Code: 4e fe e9 4d ff ff ff e8 9d c7 4e fe eb 8f e8 96 c7 4e fe e9 66
ff ff ff 90 0f 1f 44 00 00 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 <f3>
48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 f3
RIP  [<ffffffff835051c2>] __memcpy+0x12/0x20 arch/x86/lib/memcpy_64.S:37
 RSP <ffff880039ca6838>
CR2: ffff880062c6f000
---[ end trace 13b61a6864c2c008 ]---
==================================================================


There are no alloc/free stacks in the report, so maybe it is not
use-after-free but rather an out-of-bounds.

On commit 16ae16c6e5616c084168740990fc508bda6655d4 (Nov 24).