Messages in this thread | | | Date | Tue, 30 Jan 2018 22:39:08 -0800 | From | Eric Biggers <> | Subject | Re: KASAN: use-after-free Read in map_lookup_elem |
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On Fri, Jan 12, 2018 at 02:58:02PM -0800, syzbot wrote: > Hello, > > syzkaller hit the following crash on > 4147d50978df60f34d444c647dde9e5b34a4315e > git://git.cmpxchg.org/linux-mmots.git/master > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached > Raw console output is attached. > C reproducer is attached > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > for information about syzkaller reproducers > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+d9b83ca6cd9450add704@syzkaller.appspotmail.com > It will help syzbot understand when the bug is fixed. See footer for > details. > If you forward the report, please keep this part and the footer. > > audit: type=1400 audit(1515719240.359:8): avc: denied { sys_admin } for > pid=3510 comm="syzkaller886548" capability=21 > scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 > tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns > permissive=1 > audit: type=1400 audit(1515719240.417:9): avc: denied { sys_chroot } for > pid=3511 comm="syzkaller886548" capability=18 > scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 > tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns > permissive=1 > ================================================================== > BUG: KASAN: use-after-free in memcpy include/linux/string.h:344 [inline] > BUG: KASAN: use-after-free in map_lookup_elem+0x4dc/0xbd0 > kernel/bpf/syscall.c:584 > Read of size 4 at addr ffff8801bf5a9858 by task syzkaller886548/3511 > > CPU: 0 PID: 3511 Comm: syzkaller886548 Not tainted 4.15.0-rc7-mm1+ #53 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:17 [inline] > dump_stack+0x194/0x257 lib/dump_stack.c:53 > print_address_description+0x73/0x250 mm/kasan/report.c:256 > kasan_report_error mm/kasan/report.c:354 [inline] > kasan_report+0x23b/0x360 mm/kasan/report.c:412 > check_memory_region_inline mm/kasan/kasan.c:260 [inline] > check_memory_region+0x137/0x190 mm/kasan/kasan.c:267 > memcpy+0x23/0x50 mm/kasan/kasan.c:302 > memcpy include/linux/string.h:344 [inline] > map_lookup_elem+0x4dc/0xbd0 kernel/bpf/syscall.c:584 > SYSC_bpf kernel/bpf/syscall.c:1808 [inline] > SyS_bpf+0x922/0x4400 kernel/bpf/syscall.c:1782 > entry_SYSCALL_64_fastpath+0x29/0xa0 > RIP: 0033:0x440ab9 > RSP: 002b:00000000007dff68 EFLAGS: 00000203 ORIG_RAX: 0000000000000141 > RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440ab9 > RDX: 0000000000000018 RSI: 0000000020c3c000 RDI: 0000000000000001 > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000203 R12: 0000000000402290 > R13: 0000000000402320 R14: 0000000000000000 R15: 0000000000000000 > > Allocated by task 3510: > save_stack+0x43/0xd0 mm/kasan/kasan.c:447 > set_track mm/kasan/kasan.c:459 [inline] > kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552 > kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3607 > kmalloc include/linux/slab.h:515 [inline] > kzalloc include/linux/slab.h:704 [inline] > do_execveat_common.isra.30+0x3ea/0x22a0 fs/exec.c:1730 > do_execve fs/exec.c:1848 [inline] > SYSC_execve fs/exec.c:1929 [inline] > SyS_execve+0x39/0x50 fs/exec.c:1924 > do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285 > return_from_SYSCALL_64+0x0/0x75 > > Freed by task 3510: > save_stack+0x43/0xd0 mm/kasan/kasan.c:447 > set_track mm/kasan/kasan.c:459 [inline] > __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520 > kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527 > __cache_free mm/slab.c:3485 [inline] > kfree+0xd9/0x260 mm/slab.c:3800 > free_bprm+0x19d/0x200 fs/exec.c:1415 > do_execveat_common.isra.30+0x19e1/0x22a0 fs/exec.c:1813 > do_execve fs/exec.c:1848 [inline] > SYSC_execve fs/exec.c:1929 [inline] > SyS_execve+0x39/0x50 fs/exec.c:1924 > do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285 > return_from_SYSCALL_64+0x0/0x75 > > The buggy address belongs to the object at ffff8801bf5a97c0 > which belongs to the cache kmalloc-256 of size 256 > The buggy address is located 152 bytes inside of > 256-byte region [ffff8801bf5a97c0, ffff8801bf5a98c0) > The buggy address belongs to the page: > page:ffffea0006fd6a40 count:1 mapcount:0 mapping:ffff8801bf5a9040 index:0x0 > flags: 0x2fffc0000000100(slab) > raw: 02fffc0000000100 ffff8801bf5a9040 0000000000000000 000000010000000c > raw: ffffea0006fd6920 ffffea0006fdc520 ffff8801dac007c0 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8801bf5a9700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffff8801bf5a9780: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb > > ffff8801bf5a9800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff8801bf5a9880: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc > ffff8801bf5a9900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > > --- > This bug is generated by a dumb bot. It may contain errors. > See https://goo.gl/tpsmEJ for details. > Direct all questions to syzkaller@googlegroups.com. > > syzbot will keep track of this bug report. > If you forgot to add the Reported-by tag, once the fix for this bug is > merged > into any tree, please reply to this email with: > #syz fix: exact-commit-title > If you want to test a patch for this bug, please reply with:
#syz fix: bpf, array: fix overflow in max_entries and undefined behavior in index_mask
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