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Roman Gushchin 5f79489a73 mm: kmem: properly initialize local objcg variable in current_obj_cgroup() 
Erhard reported that the 6.7-rc1 kernel panics on boot if being
built with clang-16. The problem was not reproducible with gcc.

[    5.975049] general protection fault, probably for non-canonical address 0xf555515555555557: 0000 [#1] SMP KASAN PTI
[    5.976422] KASAN: maybe wild-memory-access in range [0xaaaaaaaaaaaaaab8-0xaaaaaaaaaaaaaabf]
[    5.977475] CPU: 3 PID: 1 Comm: systemd Not tainted 6.7.0-rc1-Zen3 #77
[    5.977860] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[    5.977860] RIP: 0010:obj_cgroup_charge_pages+0x27/0x2d5
[    5.977860] Code: 90 90 90 55 41 57 41 56 41 55 41 54 53 89 d5 41 89 f6 49 89 ff 48 b8 00 00 00 00 00 fc ff df 49 83 c7 10 4d3
[    5.977860] RSP: 0018:ffffc9000001fb18 EFLAGS: 00010a02
[    5.977860] RAX: dffffc0000000000 RBX: aaaaaaaaaaaaaaaa RCX: ffff8883eb9a8b08
[    5.977860] RDX: 0000000000000005 RSI: 0000000000400cc0 RDI: aaaaaaaaaaaaaaaa
[    5.977860] RBP: 0000000000000005 R08: 3333333333333333 R09: 0000000000000000
[    5.977860] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8883eb9a8b18
[    5.977860] R13: 1555555555555557 R14: 0000000000400cc0 R15: aaaaaaaaaaaaaaba
[    5.977860] FS:  00007f2976438b40(0000) GS:ffff8883eb980000(0000) knlGS:0000000000000000
[    5.977860] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    5.977860] CR2: 00007f29769e0060 CR3: 0000000107222003 CR4: 0000000000370eb0
[    5.977860] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    5.977860] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    5.977860] Call Trace:
[    5.977860]  <TASK>
[    5.977860]  ? __die_body+0x16/0x75
[    5.977860]  ? die_addr+0x4a/0x70
[    5.977860]  ? exc_general_protection+0x1c9/0x2d0
[    5.977860]  ? cgroup_mkdir+0x455/0x9fb
[    5.977860]  ? __x64_sys_mkdir+0x69/0x80
[    5.977860]  ? asm_exc_general_protection+0x26/0x30
[    5.977860]  ? obj_cgroup_charge_pages+0x27/0x2d5
[    5.977860]  obj_cgroup_charge+0x114/0x1ab
[    5.977860]  pcpu_alloc+0x1a6/0xa65
[    5.977860]  ? mem_cgroup_css_alloc+0x1eb/0x1140
[    5.977860]  ? cgroup_apply_control_enable+0x26b/0x7c0
[    5.977860]  mem_cgroup_css_alloc+0x23f/0x1140
[    5.977860]  cgroup_apply_control_enable+0x26b/0x7c0
[    5.977860]  ? cgroup_kn_set_ugid+0x2d/0x1a0
[    5.977860]  cgroup_mkdir+0x455/0x9fb
[    5.977860]  ? __cfi_cgroup_mkdir+0x10/0x10
[    5.977860]  kernfs_iop_mkdir+0x130/0x170
[    5.977860]  vfs_mkdir+0x405/0x530
[    5.977860]  do_mkdirat+0x188/0x1f0
[    5.977860]  __x64_sys_mkdir+0x69/0x80
[    5.977860]  do_syscall_64+0x7d/0x100
[    5.977860]  ? do_syscall_64+0x89/0x100
[    5.977860]  ? do_syscall_64+0x89/0x100
[    5.977860]  ? do_syscall_64+0x89/0x100
[    5.977860]  ? do_syscall_64+0x89/0x100
[    5.977860]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
[    5.977860] RIP: 0033:0x7f297671defb
[    5.977860] Code: 8b 05 39 7f 0d 00 bb ff ff ff ff 64 c7 00 16 00 00 00 e9 61 ff ff ff e8 23 0c 02 00 0f 1f 00 f3 0f 1e fa b88
[    5.977860] RSP: 002b:00007ffee6242bb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
[    5.977860] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f297671defb
[    5.977860] RDX: 0000000000000000 RSI: 00000000000001ed RDI: 000055c6b449f0e0
[    5.977860] RBP: 00007ffee6242bf0 R08: 000000000000000e R09: 0000000000000000
[    5.977860] R10: 0000000000000000 R11: 0000000000000246 R12: 000055c6b445db80
[    5.977860] R13: 00000000000003a0 R14: 00007f2976a68651 R15: 00000000000003a0
[    5.977860]  </TASK>
[    5.977860] Modules linked in:
[    6.014095] ---[ end trace 0000000000000000 ]---
[    6.014701] RIP: 0010:obj_cgroup_charge_pages+0x27/0x2d5
[    6.015348] Code: 90 90 90 55 41 57 41 56 41 55 41 54 53 89 d5 41 89 f6 49 89 ff 48 b8 00 00 00 00 00 fc ff df 49 83 c7 10 4d3
[    6.017575] RSP: 0018:ffffc9000001fb18 EFLAGS: 00010a02
[    6.018255] RAX: dffffc0000000000 RBX: aaaaaaaaaaaaaaaa RCX: ffff8883eb9a8b08
[    6.019120] RDX: 0000000000000005 RSI: 0000000000400cc0 RDI: aaaaaaaaaaaaaaaa
[    6.019983] RBP: 0000000000000005 R08: 3333333333333333 R09: 0000000000000000
[    6.020849] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8883eb9a8b18
[    6.021747] R13: 1555555555555557 R14: 0000000000400cc0 R15: aaaaaaaaaaaaaaba
[    6.022609] FS:  00007f2976438b40(0000) GS:ffff8883eb980000(0000) knlGS:0000000000000000
[    6.023593] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    6.024296] CR2: 00007f29769e0060 CR3: 0000000107222003 CR4: 0000000000370eb0
[    6.025279] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    6.026139] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    6.027000] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Actually the problem is caused by uninitialized local variable in
current_obj_cgroup().  If the root memory cgroup is set as an active
memory cgroup for a charging scope (as in the trace, where systemd tries
to create the first non-root cgroup, so the parent cgroup is the root
cgroup), the "for" loop is skipped and uninitialized objcg is returned,
causing a panic down the accounting stack.

The fix is trivial: initialize the objcg variable to NULL unconditionally
before the "for" loop.

[vbabka@suse.cz: remove redundant assignment]
  Link: https://lkml.kernel.org/r/4bd106d5-c3e3-6731-9a74-cff81e2392de@suse.cz
Link: https://lkml.kernel.org/r/20231116025109.3775055-1-roman.gushchin@linux.dev
Fixes: e86828e544 ("mm: kmem: scoped objcg protection")
Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/1959
Tested-by:  Erhard Furtner <erhard_f@mailbox.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Shakeel Butt <shakeelb@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-12-06 16:12:44 -08:00
arch LoongArch fixes for v6.7-rc3 2023-11-22 10:20:17 -08:00
block vfs-6.7-rc3.fixes 2023-11-24 09:45:40 -08:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression in ahash and hides the Kconfig sub-options for the jitter RNG. 2023-11-09 17:04:58 -08:00
Documentation Including fixes from bpf. 2023-11-23 10:40:13 -08:00
drivers drm fixes for 6.7-rc3 2023-11-24 09:36:33 -08:00
fs AFS Fixes 2023-11-24 10:40:03 -08:00
include hugetlb: fix null-ptr-deref in hugetlb_vma_lock_write 2023-12-06 16:12:43 -08:00
init As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
io_uring io_uring: fix off-by one bvec index 2023-11-20 15:21:38 -07:00
ipc Many singleton patches against the MM code. The patch series which are 2023-11-02 19:38:47 -10:00
kernel Including fixes from bpf. 2023-11-23 10:40:13 -08:00
lib vfs-6.7-rc3.fixes 2023-11-24 09:45:40 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: kmem: properly initialize local objcg variable in current_obj_cgroup() 2023-12-06 16:12:44 -08:00
net tls: fix NULL deref on tls_sw_splice_eof() with empty record 2023-11-23 08:51:45 -08:00
rust Kbuild updates for v6.7 2023-11-04 08:07:19 -10:00
samples Landlock updates for v6.7-rc1 2023-11-03 09:28:53 -10:00
scripts Kbuild fixes for v6.7 2023-11-19 13:54:28 -08:00
security + Features 2023-11-03 09:48:17 -10:00
sound sound fixes for 6.7-rc2 2023-11-17 09:05:31 -05:00
tools Including fixes from bpf. 2023-11-23 10:40:13 -08:00
usr arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: generate kernel.spec in rpmbuild/SPECS/ 2023-10-03 20:49:09 +09:00
.mailmap As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add Andrew Morton for lib/* 2023-12-06 16:12:43 -08:00
Makefile Linux 6.7-rc2 2023-11-19 15:02:14 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.