** Tags added: triage-g
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https://bugs.launchpad.net/bugs/1770784
Title:
ISST-LTE:KVM:Ubuntu1804:BostonLC:boslcp4g4:ubuntu1604:P8 compat: guest
crashes in apparmor_file_alloc_security()
Status in The Ubuntu-power-systems project:
Triaged
Status in linux package in Ubuntu:
New
Bug description:
Test was running an Ubuntu 16.04 guest with a Ubuntu 18.04 host when
the guest dumped a vmcore.
According to the dump, the crash is actually a BUG_ON() raised from
apparmor_file_alloc_security() having called aa_begin_current_label()
which calls aa_current_raw_label() that in turn calls
aa_cred_raw_label() where the BUG_ON() resides:
static inline struct aa_label *aa_cred_raw_label(const struct cred *cred)
{
struct aa_task_ctx *ctx = cred_ctx(cred);
BUG_ON(!ctx || !ctx->label);
return ctx->label;
}
Now, the warnings we previously had seen raised from aa_file_perm()
may have been related since rcu_dereference() as fctx->label is NULL.
fctx = file_ctx(file);
rcu_read_lock();
flabel = rcu_dereference(fctx->label);
AA_BUG(!flabel);
KERNEL: /usr/lib/debug/boot/vmlinux-4.4.0-124-generic
DUMPFILE: dump.201805110830 [PARTIAL DUMP]
CPUS: 32
DATE: Fri May 11 06:30:35 2018
UPTIME: 03:40:43
LOAD AVERAGE: 102.77, 103.38, 100.54
TASKS: 862
NODENAME: boslcp4g4
RELEASE: 4.4.0-124-generic
VERSION: #148-Ubuntu SMP Wed May 2 13:02:22 UTC 2018
MACHINE: ppc64le (2134 Mhz)
MEMORY: 16 GB
PANIC: "kernel BUG at
/build/linux-VRGJAN/linux-4.4.0/security/apparmor/include/context.h:69!"
PID: 18397
COMMAND: "chgrp"
TASK: c00000035be322c0 [THREAD_INFO: c00000035b5c0000]
CPU: 10
STATE: TASK_RUNNING (PANIC)
crash> bt
PID: 18397 TASK: c00000035be322c0 CPU: 10 COMMAND: "chgrp"
#0 [c00000035b5c3430] crash_kexec at c000000000176274
#1 [c00000035b5c35d0] die at c000000000020ef8
#2 [c00000035b5c3660] _exception at c000000000021244
#3 [c00000035b5c37f0] program_check_common at c000000000006208
Program Check [700] exception frame:
R0: c0000000004923e4 R1: c00000035b5c3ae0 R2: c0000000015fa700
R3: c0000000fcd01a00 R4: 0000000000000001 R5: ffffffffffffffc0
R6: c0000000fcd01b00 R7: 00000003fe8d0000 R8: c00000000163a700
R9: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000
R12: c0000000004fd880 R13: c000000007b06400 R14: 0000000000000000
R15: 0000000000000000 R16: 0000000000000013 R17: 0000000000000000
R18: 00003fffb7501468 R19: 0000000000000000 R20: 00003fffb74ff7e0
R21: 0000000000000000 R22: 0000000000000000 R23: 00003fffdf3cbd40
R24: ffffffff90000001 R25: 0000000000000041 R26: fffffffffffff000
R27: c00000035b5c3dd0 R28: c0000000016342f8 R29: c0000000fcd01a00
R30: c0000000fcd01a00 R31: 0000000000000000
NIP: c0000000004fd8c8 MSR: 8000000000029033 OR3: c0000000004923e0
CTR: c0000000004fd880 LR: c0000000004923e4 XER: 0000000000000000
CCR: 0000000024004248 MQ: 0000000000000001 DAR: c000000328004288
DSISR: c00000035b5c39e0 Syscall Result: 0000000000000000
#4 [c00000035b5c3ae0] apparmor_file_alloc_security at c0000000004fd8c8
[Link Register] [c00000035b5c3ae0] security_file_alloc at c0000000004923e4
#5 [c00000035b5c3b50] security_file_alloc at c0000000004923e4 (unreliable)
#6 [c00000035b5c3b90] get_empty_filp at c0000000002e7010
#7 [c00000035b5c3c10] path_openat at c0000000002faa2c
#8 [c00000035b5c3c90] do_filp_open at c0000000002fc9bc
#9 [c00000035b5c3db0] do_sys_open at c0000000002e3150
#10 [c00000035b5c3e30] system_call at c000000000009484
System Call [c01] exception frame:
R0: 0000000000000005 R1: 00003fffdf3cb8c0 R2: 00003fffb7507e00
R3: 00000100270514b0 R4: 0000000000080000 R5: 00003fffb7501ef8
R6: 0000000000000008 R7: ffffffff90000001 R8: 00003fffdf3cbd40
R9: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000
R12: 0000000000000000 R13: 00003fffb750a190
NIP: 00003fffb74dbdac MSR: 800000000280f033 OR3: 00000100270514b0
CTR: 0000000000000000 LR: 00003fffb74b7034 XER: 0000000000000000
CCR: 0000000044004442 MQ: 0000000000000001 DAR: 00003fffb7480000
DSISR: 0000000040000000 Syscall Result: fffffffffffffffe
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