zram: Unable to handle kernel NULL pointer dereference at virtual address

[Naresh Kamboju]

While running kselftest zram test case on qemu arm this kernel warning.
This has been reported on stable rc 5.4, 5.5 and 5.6 and mainline and next.

[ 1277.176612] kselftest: Running tests in zram
[ 1277.375891] zram: Added device: zram0
[ 1278.505516] zram0: detected capacity change from 0 to 2097152
[ 1278.545644] 8<--- cut here ---
[ 1278.547036] Unable to handle kernel NULL pointer dereference at
virtual address 00000000
[ 1278.550494] pgd = 385dcf93
[ 1278.551571] [00000000] *pgd=68116003, *pmd=1352f5003
[ 1278.553632] Internal error: Oops: 207 [#1] SMP ARM
[ 1278.555463] Modules linked in: zram act_mirred cls_u32 nf_tables
nfnetlink sch_etf sit ip_tables x_tables cls_bpf sch_fq algif_hash
crc32_arm_ce sha2_arm_ce sha256_arm sha1_arm_ce sha1_arm aes_arm_ce
crypto_simd fuse [last unloaded: test_user_copy]
[ 1278.564699] CPU: 0 PID: 11598 Comm: mkfs.ext4 Not tainted 5.4.31-rc2 #1
[ 1278.567731] Hardware name: Generic DT based system
[ 1278.569977] PC is at zs_map_object+0xc8/0x2ac
[ 1278.572001] LR is at 0xe6058000
[ 1278.573603] pc : [<c0696858>]    lr : [<e6058000>]    psr: 600d0013
[ 1278.576602] sp : e6059a40  ip : 00000000  fp : e6059a84
[ 1278.579066] r10: 00000000  r9 : 00000002  r8 : 00000000
[ 1278.581600] r7 : ecff9000  r6 : ffed05e0  r5 : c20086c8  r4 : e4907000
[ 1278.584686] r3 : ecec95e0  r2 : c2842040  r1 : 00000030  r0 : 39aca001
[ 1278.587767] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
[ 1278.591171] Control: 30c5383d  Table: 66f8d780  DAC: fffffffd
[ 1278.593918] Process mkfs.ext4 (pid: 11598, stack limit = 0xb0888730)
[ 1278.596941] Stack: (0xe6059a40 to 0xe605a000)
[ 1278.599017] 9a40: c08c1e80 efec95e0 e6059aa8 e6059a58 c04228c4
bf1b31a7 e6059a84 e64bf400
[ 1278.602884] 9a60: d89c2000 00000008 e544f000 e5713680 c20086c8
e544f000 e6059adc e6059a88
[ 1278.606739] 9a80: bf0bad70 c069679c 00000000 00000001 ed496460
00000001 e55e8000 00017e3b
[ 1278.610593] 9aa0: 00000001 c20086c8 00000041 bf1b31a7 00000000
00000000 00001000 00000001
[ 1278.614445] 9ac0: 00001000 e182d840 e64bf400 00001000 e6059b34
e6059ae0 bf0bb56c bf0ba9a4
[ 1278.618312] 9ae0: e182d840 c20086c8 c04cdd4c 00000000 c20086c8
00000000 ed496460 00001000
[ 1278.622227] 9b00: 00000000 bf1b31a7 c064f294 e55e8000 ffffe000
e182d840 00000000 c2043828
[ 1278.626154] 9b20: ffffffff c21db2a0 e6059b94 e6059b38 c091fc7c
bf0bb3d8 c040f2a0 c040dca4
[ 1278.629802] 9b40: c20086c8 00000000 c20086c8 e6059b54 c06ee318
00000000 00000000 00000000
[ 1278.633759] 9b60: 00000000 bf1b31a7 c04cdf38 c20086c8 e182d840
00000801 00000800 00000008
[ 1278.637713] 9b80: 00000000 e58dfc68 e6059c04 e6059b98 c091ffc0
c091fb70 c05713c8 e182d840
[ 1278.641609] 9ba0: e54dc038 00001000 00000000 c06ee318 e54dc04c
00000000 e6059c04 e6059bc8
[ 1278.645549] 9bc0: c06ee0b0 c04cdb0c 00000001 00000000 c06ee318
bf1b31a7 00000000 e5a88580
[ 1278.649501] 9be0: e182d840 00000801 00000800 00000000 00000000
e58dfc68 e6059c2c e6059c08
[ 1278.653423] 9c00: c06ee354 c091ff78 00000001 e5a88580 e5a88580
e6059e58 00000800 00000000
[ 1278.657215] 9c20: e6059ca4 e6059c30 c06ee700 c06ee1c4 e6059e58
00000000 c06eeda0 e6059c48
[ 1278.661069] 9c40: c040dd24 c06f248c 00001000 c06ec500 c1bb920c
00000000 c20086c8 e6059e58
[ 1278.664917] 9c60: 00000800 ed496460 c140993c 00000000 e6059ca4
bf1b31a7 c05713c8 e58dfc68
[ 1278.668758] 9c80: ed496460 600d0013 e58dfd0c c06f2564 00000001
00000000 e6059cec e6059ca8
[ 1278.672618] 9ca0: c06eeda0 c06ee390 c06ec500 00000000 c06f2564
00000001 e6059e58 c06f248c
[ 1278.676447] 9cc0: e54df048 e58dfdd8 00000002 c1b9e48c e6059d5c
00000001 e6059e58 e58dfdd8
[ 1278.680295] 9ce0: e6059cfc e6059cf0 c06f2564 c06eec1c e6059d14
e6059d00 c05f9820 c06f254c
[ 1278.684100] 9d00: ed496460 00000002 e6059dcc e6059d18 c05fd4bc
c05f9808 00000002 00000001
[ 1278.689217] 9d20: e6059d5c 00000000 00000001 c20086c8 c21dafe7
00000002 00000000 ffffffff
[ 1278.693068] 9d40: e58dfdd8 c05f97fc c20086f4 ffffe000 c21dd694
00000010 000001f4 c06f000f
[ 1278.696929] 9d60: ed6dcb50 ed496460 ed723590 ed6ef630 ed6e97e0
ed728360 ed726890 ed5b03d0
[ 1278.700775] 9d80: ed7841c0 ed451070 ed77b400 ed71fa80 ed493fd0
ed6f5a20 ed6a4570 bf1b31a7
[ 1278.704586] 9da0: ed723590 c20086c8 e58dfdd8 e6059e58 c1bacbec
c20086c8 c05f97fc e58dfdd8
[ 1278.708401] 9dc0: e6059e04 e6059dd0 c05fd8c8 c05fd28c e6059dd0
e6059dd0 e6059dd8 e6059dd8
[ 1278.712208] 9de0: 00000000 bf1b31a7 e58dfc68 e6059e58 e58dfdd8
ffffffff e6059e14 e6059e08
[ 1278.716078] 9e00: c06f2514 c05fd870 e6059e54 e6059e18 c05fe524
c06f2508 e6059e54 e6059e28
[ 1278.719910] 9e20: c06da1ac c1410518 c141015c bf1b31a7 c20086c8
e58dfc68 ffffffff 7fffffff
[ 1278.723755] 9e40: 00000000 00000000 e6059ecc e6059e58 c05f1570
c05fe4d4 7ffffffe 00000000
[ 1278.727581] 9e60: 00000000 00000000 ffffffff 7fffffff 00000001
00000000 00000000 00000000
[ 1278.731409] 9e80: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 bf1b31a7
[ 1278.735228] 9ea0: e6059f34 ffffffff e58dfdd8 e676d7c0 7fffffff
00000000 00000000 00000076
[ 1278.739109] 9ec0: e6059f04 e6059ed0 c05f2cac c05f1480 ffffffff
7fffffff 00000001 00000000
[ 1278.742970] 9ee0: e676d7c8 ffffffff 7fffffff e58dfc68 c04011c4
e6058000 e6059f2c e6059f08
[ 1278.746848] 9f00: c06f1f20 c05f2c58 ffffffff 7fffffff e676d7c0
e676d7c0 00000000 ffffffff
[ 1278.750806] 9f20: e6059f64 e6059f30 c06e437c c06f1f00 ffffffff
7fffffff 00000000 00000000
[ 1278.754698] 9f40: c06c6a98 c06c59dc e676d7c0 e676d7c0 00000000
00000076 e6059f94 e6059f68
[ 1278.758553] 9f60: c06e4444 c06e433c ffffffff 7fffffff 00000000
c0401100 e6059fac 0003b8f0
[ 1278.762465] 9f80: 0003b7e8 00000000 e6059fa4 e6059f98 c06e4764
c06e4404 00000000 e6059fa8
[ 1278.766315] 9fa0: c0401000 c06e4754 0003b8f0 0003b7e8 00000005
00046a80 00000064 00000000
[ 1278.770146] 9fc0: 0003b8f0 0003b7e8 00000000 00000076 00000000
bea318f8 bea318e8 bea318f0
[ 1278.773976] 9fe0: b6da85ec bea31898 b6eea0d0 b6da8614 600d0010
00000005 00000000 00000000
[ 1278.777818] Backtrace:
[ 1278.779056] [<c0696790>] (zs_map_object) from [<bf0bad70>]
(zram_bvec_rw.constprop.2+0x3d8/0xa34 [zram])
[ 1278.783562]  r10:e544f000 r9:c20086c8 r8:e5713680 r7:e544f000
r6:00000008 r5:d89c2000
[ 1278.787300]  r4:e64bf400
[ 1278.788619] [<bf0ba998>] (zram_bvec_rw.constprop.2 [zram]) from
[<bf0bb56c>] (zram_make_request+0x1a0/0x494 [zram])
[ 1278.793537]  r10:00001000 r9:e64bf400 r8:e182d840 r7:00001000
r6:00000001 r5:00001000
[ 1278.797252]  r4:00000000
[ 1278.798512] [<bf0bb3cc>] (zram_make_request [zram]) from
[<c091fc7c>] (generic_make_request+0x118/0x408)
[ 1278.803535]  r10:c21db2a0 r9:ffffffff r8:c2043828 r7:00000000
r6:e182d840 r5:ffffe000
[ 1278.807294]  r4:e55e8000
[ 1278.808572] [<c091fb64>] (generic_make_request) from [<c091ffc0>]
(submit_bio+0x54/0x1c4)
[ 1278.812454]  r10:e58dfc68 r9:00000000 r8:00000008 r7:00000800
r6:00000801 r5:e182d840
[ 1278.816137]  r4:c20086c8
[ 1278.817417] [<c091ff6c>] (submit_bio) from [<c06ee354>]
(submit_bh_wbc+0x19c/0x1cc)
[ 1278.821098]  r10:e58dfc68 r9:00000000 r8:00000000 r7:00000800
r6:00000801 r5:e182d840
[ 1278.824858]  r4:e5a88580
[ 1278.826122] [<c06ee1b8>] (submit_bh_wbc) from [<c06ee700>]
(__block_write_full_page+0x37c/0x6f0)
[ 1278.830284]  r9:00000000 r8:00000800 r7:e6059e58 r6:e5a88580
r5:e5a88580 r4:00000001
[ 1278.833968] [<c06ee384>] (__block_write_full_page) from
[<c06eeda0>] (block_write_full_page+0x190/0x198)
[ 1278.838448]  r10:00000000 r9:00000001 r8:c06f2564 r7:e58dfd0c
r6:600d0013 r5:ed496460
[ 1278.842157]  r4:e58dfc68
[ 1278.843410] [<c06eec10>] (block_write_full_page) from [<c06f2564>]
(blkdev_writepage+0x24/0x28)
[ 1278.847528]  r10:e58dfdd8 r9:e6059e58 r8:00000001 r7:e6059d5c
r6:c1b9e48c r5:00000002
[ 1278.851241]  r4:e58dfdd8
[ 1278.852509] [<c06f2540>] (blkdev_writepage) from [<c05f9820>]
(__writepage+0x24/0x5c)
[ 1278.856201] [<c05f97fc>] (__writepage) from [<c05fd4bc>]
(write_cache_pages+0x23c/0x5e4)
[ 1278.860010]  r5:00000002 r4:ed496460
[ 1278.861756] [<c05fd280>] (write_cache_pages) from [<c05fd8c8>]
(generic_writepages+0x64/0x90)
[ 1278.865824]  r10:e58dfdd8 r9:c05f97fc r8:c20086c8 r7:c1bacbec
r6:e6059e58 r5:e58dfdd8
[ 1278.869552]  r4:c20086c8
[ 1278.870805] [<c05fd864>] (generic_writepages) from [<c06f2514>]
(blkdev_writepages+0x18/0x1c)
[ 1278.874871]  r6:ffffffff r5:e58dfdd8 r4:e6059e58
[ 1278.877398] [<c06f24fc>] (blkdev_writepages) from [<c05fe524>]
(do_writepages+0x5c/0x108)
[ 1278.881292] [<c05fe4c8>] (do_writepages) from [<c05f1570>]
(__filemap_fdatawrite_range+0xfc/0x128)
[ 1278.885538]  r9:00000000 r8:00000000 r7:7fffffff r6:ffffffff
r5:e58dfc68 r4:c20086c8
[ 1278.889480] [<c05f1474>] (__filemap_fdatawrite_range) from
[<c05f2cac>] (file_write_and_wait_range+0x60/0xb4)
[ 1278.894166]  r10:00000076 r9:00000000 r8:00000000 r7:7fffffff
r6:e676d7c0 r5:e58dfdd8
[ 1278.897979]  r4:ffffffff
[ 1278.899227] [<c05f2c4c>] (file_write_and_wait_range) from
[<c06f1f20>] (blkdev_fsync+0x2c/0x58)
[ 1278.903348]  r9:e6058000 r8:c04011c4 r6:e58dfc68 r5:7fffffff r4:ffffffff
[ 1278.906618] [<c06f1ef4>] (blkdev_fsync) from [<c06e437c>]
(vfs_fsync_range+0x4c/0x8c)
[ 1278.910366]  r6:ffffffff r5:00000000 r4:e676d7c0
[ 1278.912646] [<c06e4330>] (vfs_fsync_range) from [<c06e4444>]
(do_fsync+0x4c/0x74)
[ 1278.916241]  r7:00000076 r6:00000000 r5:e676d7c0 r4:e676d7c0
[ 1278.918974] [<c06e43f8>] (do_fsync) from [<c06e4764>] (sys_fsync+0x1c/0x20)
[ 1278.922350]  r6:00000000 r5:0003b7e8 r4:0003b8f0
[ 1278.924675] [<c06e4748>] (sys_fsync) from [<c0401000>]
(ret_fast_syscall+0x0/0x28)
[ 1278.928344] Exception stack(0xe6059fa8 to 0xe6059ff0)
[ 1278.930781] 9fa0:                   0003b8f0 0003b7e8 00000005
00046a80 00000064 00000000
[ 1278.934719] 9fc0: 0003b8f0 0003b7e8 00000000 00000076 00000000
bea318f8 bea318e8 bea318f0
[ 1278.938627] 9fe0: b6da85ec bea31898 b6eea0d0 b6da8614
[ 1278.941101] Code: e5927000 e0060391 e0873006 e5938018 (e5982000)
[ 1278.944270] ---[ end trace 2de575b2ace669f8 ]---
[ 1278.947457] note: mkfs.ext4[11598] exited with preempt_count 2

Full test log,
https://lkft.validation.linaro.org/scheduler/job/1350791#L15827
https://lkft.validation.linaro.org/scheduler/job/1351118#L15840
https://lkft.validation.linaro.org/scheduler/job/1350630#L16995

-- 
Linaro LKFT
https://lkft.linaro.org