MPI: mpi too large (32768 bits)
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BUG: KASAN: use-after-free in mpi_free+0x117/0x150 lib/mpi/mpiutil.c:114
Read of size 4 at addr ffff8801d49cff50 by task syz-executor7/20212

CPU: 1 PID: 20212 Comm: syz-executor7 Not tainted 4.14.0+ #176
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:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 mpi_free+0x117/0x150 lib/mpi/mpiutil.c:114
 dh_clear_params crypto/dh.c:26 [inline]
 dh_free_ctx crypto/dh.c:34 [inline]
 dh_exit_tfm+0x3d/0x140 crypto/dh.c:161
 crypto_kpp_exit_tfm+0x52/0x70 crypto/kpp.c:63
 crypto_exit_ops crypto/api.c:314 [inline]
 crypto_destroy_tfm+0xb9/0x2e0 crypto/api.c:578
 crypto_free_kpp include/crypto/kpp.h:165 [inline]
 __keyctl_dh_compute+0x1087/0x1a00 security/keys/dh.c:412
 keyctl_dh_compute+0xac/0xf3 security/keys/dh.c:434
 SYSC_keyctl security/keys/keyctl.c:1745 [inline]
 SyS_keyctl+0x72/0x2c0 security/keys/keyctl.c:1641
 do_syscall_64+0x26c/0x920 arch/x86/entry/common.c:285
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x452879
RSP: 002b:00007f543c225be8 EFLAGS: 00000212 ORIG_RAX: 00000000000000fa
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452879
RDX: 000000002001cf83 RSI: 000000002000dff4 RDI: 0000000000000017
RBP: 00000000000003ae R08: 0000000020b24000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000212 R12: 00000000006f38f0
R13: 00000000ffffffff R14: 00007f543c2266d4 R15: 0000000000000000

Allocated by task 20212:
 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:551
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3628
 kmalloc include/linux/slab.h:494 [inline]
 mpi_alloc+0x4b/0x230 lib/mpi/mpiutil.c:34
 mpi_read_raw_data+0x1e5/0x440 lib/mpi/mpicoder.c:57
 dh_set_params crypto/dh.c:69 [inline]
 dh_set_secret+0x257/0x600 crypto/dh.c:94
 crypto_kpp_set_secret include/crypto/kpp.h:291 [inline]
 __keyctl_dh_compute+0x9cf/0x1a00 security/keys/dh.c:333
 keyctl_dh_compute+0xac/0xf3 security/keys/dh.c:434
 SYSC_keyctl security/keys/keyctl.c:1745 [inline]
 SyS_keyctl+0x72/0x2c0 security/keys/keyctl.c:1641
 do_syscall_64+0x26c/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

Freed by task 20212:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3504 [inline]
 kfree+0xca/0x250 mm/slab.c:3821
 mpi_free+0xcb/0x150 lib/mpi/mpiutil.c:121
 dh_set_params crypto/dh.c:75 [inline]
 dh_set_secret+0x3e5/0x600 crypto/dh.c:94
 crypto_kpp_set_secret include/crypto/kpp.h:291 [inline]
 __keyctl_dh_compute+0x9cf/0x1a00 security/keys/dh.c:333
 keyctl_dh_compute+0xac/0xf3 security/keys/dh.c:434
 SYSC_keyctl security/keys/keyctl.c:1745 [inline]
 SyS_keyctl+0x72/0x2c0 security/keys/keyctl.c:1641
 do_syscall_64+0x26c/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

The buggy address belongs to the object at ffff8801d49cff40
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 16 bytes inside of
 32-byte region [ffff8801d49cff40, ffff8801d49cff60)
The buggy address belongs to the page:
page:ffffea00075273c0 count:1 mapcount:0 mapping:ffff8801d49cf000 index:0xffff8801d49cffc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d49cf000 ffff8801d49cffc1 0000000100000029
raw: ffffea00075d8760 ffffea00070cf2a0 ffff8801dac001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d49cfe00: 06 fc fc fc fc fc fc fc 06 fc fc fc fc fc fc fc
 ffff8801d49cfe80: fb fb fb fb fc fc fc fc 04 fc fc fc fc fc fc fc
>ffff8801d49cff00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                                                 ^
 ffff8801d49cff80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d49d0000: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
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