Re: [PATCH] UBI: block: Must use a mutex when using idr_alloc/idr_remove

Ezequiel Garcia
2018-01-17T20:06:44Z

On 17 January 2018 at 17:04, Richard Weinberger <richard@nod.at> wrote:
> Am Mittwoch, 17. Januar 2018, 20:46:51 CET schrieb Bradley Bolen:
>> On 01/14/2018 05:20 PM, Ezequiel Garcia wrote:
>> > On 14 January 2018 at 11:39, Boris Brezillon
>> >
>> > <boris.brezillon@free-electrons.com> wrote:
>> >> +Ezequiel
>> >>
>> >> Hi Bradley,
>> >>
>> >> On Tue, 2 Jan 2018 21:26:09 -0500
>> >>
>> >> Bradley Bolen <bradleybolen@gmail.com> wrote:
>> >>> This fixes a race condition where running ubiblock on multiple volumes
>> >>> simultaneously produces the following splat.
>> >>>
>> >>> kernel BUG at kernel-source/fs/sysfs/group.c:113!
>> >>> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>> >>> [<c01e4160>] (internal_create_group) from [<c01e43fc>]
>> >>> (sysfs_create_group+0x20/0x24)
>> >>> [<c01e43fc>] (sysfs_create_group) from [<c00e4800>]
>> >>> (blk_trace_init_sysfs+0x18/0x20)
>> >>> [<c00e4800>] (blk_trace_init_sysfs) from [<c02bc734>]
>> >>> (blk_register_queue+0x6c/0x154)
>> >>> [<c02bc734>] (blk_register_queue) from [<c02cd610>]
>> >>> (device_add_disk+0x2c8/0x450)
>> >>> [<c02cd610>] (device_add_disk) from [<c0430fac>]
>> >>> (ubiblock_create+0x254/0x2e4)
>> >>> [<c0430fac>] (ubiblock_create) from [<c0421a3c>]
>> >>> (vol_cdev_ioctl+0x3e0/0x564)
>> >>> [<c0421a3c>] (vol_cdev_ioctl) from [<c018a55c>] (vfs_ioctl+0x30/0x44)
>> >>> [<c018a55c>] (vfs_ioctl) from [<c018ad2c>] (do_vfs_ioctl+0x694/0x798)
>> >>> [<c018ad2c>] (do_vfs_ioctl) from [<c018ae74>] (SyS_ioctl+0x44/0x6c)
>> >>> [<c018ae74>] (SyS_ioctl) from [<c0010720>] (ret_fast_syscall+0x0/0x34)
>> >
>> > I'm a little confused, how does this stack trace relates to idr?
>>
>> I apologize. The commit message was a little terse. Here is the full
>> output of the issue I ran into.
>>
>> ------------[ cut here ]------------
>> block ubiblock0_3: created from ubi0:3(Partition3)
>> block ubiblock0_2: created from ubi0:2(Partition2)
>> block ubiblock0_4: created from ubi0:4(Partition4)
>> WARNING: CPU: 1 PID: 179 at kernel-source/fs/sysfs/dir.c:31
>> sysfs_warn_dup+0x68/0x88 sysfs: cannot create duplicate filename
>> '/devices/virtual/bdi/252:2' Modules linked in:
>> CPU: 1 PID: 179 Comm: ubiblock Tainted: P O
>> 4.11.12-yocto-standard-414e5550071e0ca8639b0d8fb84fed31 #1 Hardware name:
>> (Device Tree)
>> [<c0019e50>] (unwind_backtrace) from [<c0014b20>] (show_stack+0x20/0x24)
>> [<c0014b20>] (show_stack) from [<c02e2618>] (dump_stack+0x78/0x94)
>> [<c02e2618>] (dump_stack) from [<c002ae6c>] (__warn+0xf0/0x110)
>> [<c002ae6c>] (__warn) from [<c002aee0>] (warn_slowpath_fmt+0x54/0x74)
>> [<c002aee0>] (warn_slowpath_fmt) from [<c01e2028>]
>> (sysfs_warn_dup+0x68/0x88) [<c01e2028>] (sysfs_warn_dup) from [<c01e2120>]
>> (sysfs_create_dir_ns+0x84/0x94) [<c01e2120>] (sysfs_create_dir_ns) from
>> [<c02e44cc>] (kobject_add_internal+0x130/0x2f8) [<c02e44cc>]
>> (kobject_add_internal) from [<c02e4730>] (kobject_add+0x9c/0xb8)
>> [<c02e4730>] (kobject_add) from [<c03b2744>] (device_add+0xfc/0x56c)
>> [<c03b2744>] (device_add) from [<c03b2d38>]
>> (device_create_groups_vargs+0x90/0xd0) [<c03b2d38>]
>> (device_create_groups_vargs) from [<c03b2dac>]
>> (device_create_vargs+0x34/0x3c) [<c03b2dac>] (device_create_vargs) from
>> [<c01301e4>] (bdi_register+0x70/0x1cc) [<c01301e4>] (bdi_register) from
>> [<c01308f8>] (bdi_register_owner+0x3c/0x7c) [<c01308f8>]
>> (bdi_register_owner) from [<c02cec04>] (device_add_disk+0x114/0x44c)
>> [<c02cec04>] (device_add_disk) from [<c0436ec8>]
>> (ubiblock_create+0x284/0x2e0) [<c0436ec8>] (ubiblock_create) from
>> [<c0427bb8>] (vol_cdev_ioctl+0x450/0x554) [<c0427bb8>] (vol_cdev_ioctl)
>> from [<c0189110>] (vfs_ioctl+0x30/0x44) [<c0189110>] (vfs_ioctl) from
>> [<c01892e0>] (do_vfs_ioctl+0xa0/0x790) [<c01892e0>] (do_vfs_ioctl) from
>> [<c0189a14>] (SyS_ioctl+0x44/0x68) [<c0189a14>] (SyS_ioctl) from
>> [<c0010640>] (ret_fast_syscall+0x0/0x34) ---[ end trace e541910253daa337
>> ]---
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 179 at kernel-source/lib/kobject.c:240
>> kobject_add_internal+0x1ec/0x2f8 kobject_add_internal failed for 252:2 with
>> -EEXIST, don't try to register things with the same name in the same direc
>> tory.
>> Modules linked in:
>> CPU: 1 PID: 179 Comm: ubiblock Tainted: P W O
>> 4.11.12-yocto-standard-414e5550071e0ca8639b0d8fb84fed31 #1 Hardware name:
>> (Device Tree)
>> [<c0019e50>] (unwind_backtrace) from [<c0014b20>] (show_stack+0x20/0x24)
>> [<c0014b20>] (show_stack) from [<c02e2618>] (dump_stack+0x78/0x94)
>> [<c02e2618>] (dump_stack) from [<c002ae6c>] (__warn+0xf0/0x110)
>> [<c002ae6c>] (__warn) from [<c002aee0>] (warn_slowpath_fmt+0x54/0x74)
>> [<c002aee0>] (warn_slowpath_fmt) from [<c02e4588>]
>> (kobject_add_internal+0x1ec/0x2f8) [<c02e4588>] (kobject_add_internal) from
>> [<c02e4730>] (kobject_add+0x9c/0xb8) [<c02e4730>] (kobject_add) from
>> [<c03b2744>] (device_add+0xfc/0x56c) [<c03b2744>] (device_add) from
>> [<c03b2d38>] (device_create_groups_vargs+0x90/0xd0) [<c03b2d38>]
>> (device_create_groups_vargs) from [<c03b2dac>]
>> (device_create_vargs+0x34/0x3c) [<c03b2dac>] (device_create_vargs) from
>> [<c01301e4>] (bdi_register+0x70/0x1cc) [<c01301e4>] (bdi_register) from
>> [<c01308f8>] (bdi_register_owner+0x3c/0x7c) [<c01308f8>]
>> (bdi_register_owner) from [<c02cec04>] (device_add_disk+0x114/0x44c)
>> [<c02cec04>] (device_add_disk) from [<c0436ec8>]
>> (ubiblock_create+0x284/0x2e0) [<c0436ec8>] (ubiblock_create) from
>> [<c0427bb8>] (vol_cdev_ioctl+0x450/0x554) [<c0427bb8>] (vol_cdev_ioctl)
>> from [<c0189110>] (vfs_ioctl+0x30/0x44) [<c0189110>] (vfs_ioctl) from
>> [<c01892e0>] (do_vfs_ioctl+0xa0/0x790) [<c01892e0>] (do_vfs_ioctl) from
>> [<c0189a14>] (SyS_ioctl+0x44/0x68) [<c0189a14>] (SyS_ioctl) from
>> [<c0010640>] (ret_fast_syscall+0x0/0x34) ---[ end trace e541910253daa338
>> ]---
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 179 at kernel-source/fs/sysfs/dir.c:31
>> sysfs_warn_dup+0x68/0x88 sysfs: cannot create duplicate filename
>> '/dev/block/252:2'
>> Modules linked in:
>> CPU: 1 PID: 179 Comm: ubiblock Tainted: P W O
>> 4.11.12-yocto-standard-414e5550071e0ca8639b0d8fb84fed31 #1 Hardware name:
>> (Device Tree)
>> [<c0019e50>] (unwind_backtrace) from [<c0014b20>] (show_stack+0x20/0x24)
>> [<c0014b20>] (show_stack) from [<c02e2618>] (dump_stack+0x78/0x94)
>> [<c02e2618>] (dump_stack) from [<c002ae6c>] (__warn+0xf0/0x110)
>> [<c002ae6c>] (__warn) from [<c002aee0>] (warn_slowpath_fmt+0x54/0x74)
>> [<c002aee0>] (warn_slowpath_fmt) from [<c01e2028>]
>> (sysfs_warn_dup+0x68/0x88) [<c01e2028>] (sysfs_warn_dup) from [<c01e23c8>]
>> (sysfs_do_create_link_sd+0xa0/0xbc) [<c01e23c8>] (sysfs_do_create_link_sd)
>> from [<c01e2418>] (sysfs_create_link+0x34/0x44) [<c01e2418>]
>> (sysfs_create_link) from [<c03b2a74>] (device_add+0x42c/0x56c) [<c03b2a74>]
>> (device_add) from [<c02cec50>] (device_add_disk+0x160/0x44c) [<c02cec50>]
>> (device_add_disk) from [<c0436ec8>] (ubiblock_create+0x284/0x2e0)
>> [<c0436ec8>] (ubiblock_create) from [<c0427bb8>]
>> (vol_cdev_ioctl+0x450/0x554) [<c0427bb8>] (vol_cdev_ioctl) from
>> [<c0189110>] (vfs_ioctl+0x30/0x44) [<c0189110>] (vfs_ioctl) from
>> [<c01892e0>] (do_vfs_ioctl+0xa0/0x790) [<c01892e0>] (do_vfs_ioctl) from
>> [<c0189a14>] (SyS_ioctl+0x44/0x68) [<c0189a14>] (SyS_ioctl) from
>> [<c0010640>] (ret_fast_syscall+0x0/0x34) ---[ end trace e541910253daa339
>> ]---
>> ubiblock (179): undefined instruction: pc=c01e26cc
>> CPU: 1 PID: 179 Comm: ubiblock Tainted: P W O
>> 4.11.12-yocto-standard-414e5550071e0ca8639b0d8fb84fed31 #1 Hardware name:
>> (Device Tree)
>> task: c185d780 task.stack: d053a000
>> PC is at internal_create_group+0x3c/0x2a0
>> LR is at sysfs_create_group+0x20/0x24
>> pc : [<c01e26cc>] lr : [<c01e2950>] psr: 60000013
>> sp : d053bd38 ip : d053bd70 fp : d053bd6c
>> r10: c095fddc r9 : 00000000 r8 : c1b59c00
>> r7 : c1b59870 r6 : c090f488 r5 : c09276f8 r4 : 00000000
>> r3 : 00000000 r2 : c09276f8 r1 : 00000000 r0 : c1b59870
>> Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
>> Control: 30c5383d Table: 104b6840 DAC: ffab73de
>> Code: e89da8f0 e1a0c00d e92ddff0 e24cb004 e24dd00c e52de004 e8bd4000
>> e2507000 e1a09001 e1a05002 0a000004 e3510000 e59 74018 1a000002 e3540000
>> 1a000002 (e7f001f2) e3540000 0a00000f e595300c e5951000 e3530000 1a00000d
>> e5953010 e3530000 1 a00000a e59f2220 e3510000 e5973000 e59f0218 01a01002
>> e59f2214
>> ------------[ cut here ]------------
>> kernel BUG at kernel-source/fs/sysfs/group.c:113!
>> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>> -----------[ user debug ]-----------
>> Current process: ubiblock pid=179
>> Running on CPU1 (2 online)
>>
>> current=c185d780 preempt_count=0x0
>> CPU: 1 PID: 179 Comm: ubiblock Tainted: P W O
>> 4.11.12-yocto-standard-414e5550071e0ca8639b0d8fb84fed31 #1 Hardware name:
>> (Device Tree)
>> task: c185d780 task.stack: d053a000
>> PC is at 0x4b767d8c
>> LR is at 0x10b78
>> pc : [<4b767d8c>] lr : [<00010b78>] psr: 60000010
>> sp : be73fc34 ip : 4b767d80 fp : 00000000
>> r10: 00000003 r9 : be73fdb4 r8 : 00000000
>> r7 : 00000036 r6 : 00000003 r5 : 000250a8 r4 : ffffffff
>> r3 : 00000001 r2 : 22eea600 r1 : 40804f07 r0 : 00000003
>> Flags: nZCv IRQs on FIQs on Mode USER_32 ISA ARM Segment user
>> Control: 30c5383d Table: 104b6840 DAC: ffab73de
>>
>> Memory Maps:
>> 00010-
>> 00015
>> ubiblock
>>
>> 00024-
>> 00026
>> ubiblock
>>
>> 00026-
>> 00047
>>
>> 4b660-
>> 4b67f
>> ld-2
>>
>> 4b68e-
>> 4b690
>> ld-2
>>
>> 4b6a0-
>> 4b7da
>> libc-2
>>
>> 4b7da-
>> 4b7dc
>>
>> b6bad-
>> b6baf
>>
>> be71f-
>> be740
>>
>> beb84-
>> ---------[ end user debug ]---------
>> Modules linked in:
>> CPU: 1 PID: 179 Comm: ubiblock Tainted: P W O
>> 4.11.12-yocto-standard-414e5550071e0ca8639b0d8fb84fed31 #1 Hardware name:
>> (Device Tree)
>> task: c185d780 task.stack: d053a000
>> PC is at internal_create_group+0x3c/0x2a0
>> LR is at sysfs_create_group+0x20/0x24
>> pc : [<c01e26cc>] lr : [<c01e2950>] psr: 60000013
>> sp : d053bd38 ip : d053bd70 fp : d053bd6c
>> r10: c095fddc r9 : 00000000 r8 : c1b59c00
>> r7 : c1b59870 r6 : c090f488 r5 : c09276f8 r4 : 00000000
>> r3 : 00000000 r2 : c09276f8 r1 : 00000000 r0 : c1b59870
>> Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
>> Control: 30c5383d Table: 104b6840 DAC: ffab73de
>> Process ubiblock (pid: 179, stack limit = 0xd053a210)
>> Stack: (0xd053bd38 to 0xd053c000)
>> bd20: d053bd5c
>> d053bd48 bd40: c00731c8 d0bd9e00 c1b59800 c090f488 c1b59868 c1b59c00
>> c1b5980c c095fddc bd60: d053bd7c d053bd70 c01e2950 c01e269c d053bd8c
>> d053bd80 c00e3d38 c01e293c bd80: d053bdbc d053bd90 c02bdfbc c00e3d2c
>> 00040b0c c1b59800 c1b59868 c090f488 bda0: c1b59870 c1b59c00 c1b5980c
>> c095fddc d053be14 d053bdc0 c02cec84 c02bdef0 bdc0: c02ce6cc c1b59800
>> d053bdfc d053bdd8 0fc00002 c0053478 00000000 1f518000 bde0: d053be1c
>> 00040b0c 00000000 c1b11e40 00000000 c1b59800 c095fda4 d053be60 be00:
>> c1b11e8c c095fddc d053be54 d053be18 c0436ec8 c02ceafc 00000000 c1b5980c
>> be20: c01e06f0 c1b5980c 00000000 22eea600 d04b6100 d0b7cc00 d1c20000
>> c090f488 be40: d053a000 c090f488 d053bedc d053be58 c0427bb8 c0436c50
>> 00000001 00000000 be60: 00000000 0000000f 00000017 00000003 002c9000
>> 00000000 00000001 00000003 be80: 00000000 00000000 00000001 0001f000
>> 00000006 d0b7ce5c 0f700010 c005368c bea0: 9a877d41 00000007 c1aab015
>> c0755170 00000261 00040b0c d053beec 22eea600 bec0: d0b96228 c1896300
>> 00000003 22eea600 d053beec d053bee0 c0189110 c0427774 bee0: d053bf7c
>> d053bef0 c01892e0 c01890ec d053bf34 c0185224 c01954e8 c05e9a14 bf00:
>> c0185278 c1aab000 c090f488 c1896300 d0b96228 c1aab000 c1896308 00000020
>> bf20: d053bf44 d053bf30 c0185224 c0163200 00000003 c090f488 d053bf94
>> d053bf48 bf40: c0175504 c01851c4 00000000 00040b0c 00000002 00000003
>> c1896300 c1896300 bf60: 40804f07 22eea600 d053a000 00000000 d053bfa4
>> d053bf80 c0189a14 c018924c bf80: ffffffff 000250a8 00000003 00000036
>> c00107e4 d053a000 00000000 d053bfa8 bfa0: c0010640 c01899dc ffffffff
>> 000250a8 00000003 40804f07 22eea600 00000001 bfc0: ffffffff 000250a8
>> 00000003 00000036 00000000 be73fdb4 00000003 00000000 bfe0: 4b767d80
>> be73fc34 00010b78 4b767d8c 60000010 00000003 e675ff3a 2a3139dd [<c01e26cc>]
>> (internal_create_group) from [<c01e2950>] (sysfs_create_group+0x20/0x24)
>> [<c01e2950>] (sysfs_create_group) from [<c00e3d38>]
>> (blk_trace_init_sysfs+0x18/0x20) [<c00e3d38>] (blk_trace_init_sysfs) from
>> [<c02bdfbc>] (blk_register_queue+0xd8/0x154) [<c02bdfbc>]
>> (blk_register_queue) from [<c02cec84>] (device_add_disk+0x194/0x44c)
>> [<c02cec84>] (device_add_disk) from [<c0436ec8>]
>> (ubiblock_create+0x284/0x2e0) [<c0436ec8>] (ubiblock_create) from
>> [<c0427bb8>] (vol_cdev_ioctl+0x450/0x554) [<c0427bb8>] (vol_cdev_ioctl)
>> from [<c0189110>] (vfs_ioctl+0x30/0x44) [<c0189110>] (vfs_ioctl) from
>> [<c01892e0>] (do_vfs_ioctl+0xa0/0x790) [<c01892e0>] (do_vfs_ioctl) from
>> [<c0189a14>] (SyS_ioctl+0x44/0x68) [<c0189a14>] (SyS_ioctl) from
>> [<c0010640>] (ret_fast_syscall+0x0/0x34) Code: e89da8f0 e1a0c00d e92ddff0
>> e24cb004 e24dd00c e52de004 e8bd4000 e2507000 e1a09001 e1a05002 0a000004
>> e3510000 e59 74018 1a000002 e3540000 1a000002 (e7f001f2) e3540000 0a00000f
>> e595300c e5951000 e3530000 1a00000d e5953010 e3530000 1 a00000a e59f2220
>> e3510000 e5973000 e59f0218 01a01002 e59f2214
>> ---[ end trace e541910253daa33a ]---
>>
>> I was able to reproduce the problem with the following script with the
>> underlying volumes already created:
>>
>> while true; do
>> for part in 2 3 4 15 24 90 91; do
>> ubiblock -c /dev/ubi0_$part &
>> done
>> sleep 2
>>
>> for part in 2 3 4 15 24 90 91; do
>> ubiblock -r /dev/ubi0_$part &
>> done
>> sleep 2
>> done
>>
>> There is a race with idr_alloc where gd->first_minor could be set to the
>> same value for two different calls to ubiblock_create. Each instance
>> calls device_add_disk with the same first_minor. device_add_disk calls
>> bdi_register_owner. The bdi_register_owner call path produces the
>> initial WARNINGS about registering the same device. However,
>> device_add_disk does not error out when bdi_register_owner returns an
>> error. The control continues until it reaches blk_register_queue which
>> eventually BUGs.
>>
>> >> Missing Fixes and Cc-stable tags.
>> >>
>> >>> Signed-off-by: Bradley Bolen <bradleybolen@gmail.com>
>> >>
>> >> Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
>> >>
>> >> BTW, just had a quick look at the code, and I think the locking can be
>> >> simplified a bit by keeping the devices_lock for the whole
>> >> ubiblock_create() operation instead of acquiring/releasing it several
>> >> times in the function (see [1]). It makes sense to do fine grained
>> >> locking when operations protected by the lock are time sensitive, but I
>> >> don't think this is the case here.
>> >
>> > Agreed. Something like this perhaps http://ix.io/E8G ?
>> > Notice that ubiblock_remove_all seemed to require locking as well.
>>
>> I tried out Ezequiel's patch and it fixes this issue as well. Note,
>> that ret needs to be defined in ubiblock_remove.
>
> Can you please have a proper patch such that I can take it? :-)
>

Bradley,

Feel free to submit a patch based on the (untested) diff I sent.
While there, you can improve the commit log with the details
you sent.
--
Ezequiel García, VanguardiaSur