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Taehee Yoo c8b81c33c5 debugfs: Check module state before warning in {full/open}_proxy_open() 
[ Upstream commit 275678e7a9 ]

When the module is being removed, the module state is set to
MODULE_STATE_GOING. At this point, try_module_get() fails.
And when {full/open}_proxy_open() is being called,
it calls try_module_get() to try to hold module reference count.
If it fails, it warns about the possibility of debugfs file leak.

If {full/open}_proxy_open() is called while the module is being removed,
it fails to hold the module.
So, It warns about debugfs file leak. But it is not the debugfs file
leak case. So, this patch just adds module state checking routine
in the {full/open}_proxy_open().

Test commands:
    #SHELL1
    while :
    do
        modprobe netdevsim
        echo 1 > /sys/bus/netdevsim/new_device
        modprobe -rv netdevsim
    done

    #SHELL2
    while :
    do
        cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
    done

Splat looks like:
[  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
[  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
[  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
[  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
[  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
[  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
[  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
[  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
[  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
[  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
[  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
[  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
[  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  298.787785][T14664] Call Trace:
[  298.788237][T14664]  do_dentry_open+0x63c/0xf50
[  298.788872][T14664]  ? open_proxy_open+0x270/0x270
[  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
[  298.790169][T14664]  ? inode_permission+0x65/0x390
[  298.790832][T14664]  path_openat+0xc45/0x2680
[  298.791425][T14664]  ? save_stack+0x69/0x80
[  298.791988][T14664]  ? save_stack+0x19/0x80
[  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
[  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
[  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
[  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
[  298.795153][T14664]  do_filp_open+0x16a/0x260
[ ... ]

Fixes: 9fd4dcece4 ("debugfs: prevent access to possibly dead file_operations at file open")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Link: https://lore.kernel.org/r/20200218043150.29447-1-ap420073@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-04-17 10:50:02 +02:00
arch x86: Don't let pgprot_modify() change the page encryption bit 2020-04-17 10:50:01 +02:00
block block: keep bdi->io_pages in sync with max_sectors_kb for stacked devices 2020-04-17 10:50:01 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: rename sm3-256 to sm3 in hash_algo_name 2020-02-28 17:22:26 +01:00
Documentation dt-bindings: net: FMan erratum A050385 2020-04-01 11:01:52 +02:00
drivers ACPI: EC: Do not clear boot_ec_is_ecdt in acpi_ec_add() 2020-04-17 10:50:01 +02:00
fs debugfs: Check module state before warning in {full/open}_proxy_open() 2020-04-17 10:50:02 +02:00
include media: rc: add keymap for Videostrong KII Pro 2020-04-17 10:49:59 +02:00
init kbuild: remove header compile test 2020-03-05 16:43:47 +01:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-28 17:22:20 +01:00
kernel dma-mapping: Fix dma_pgprot() for unencrypted coherent pages 2020-04-17 10:50:01 +02:00
lib uapi: rename ext2_swab() to swab() and share globally in swab.h 2020-04-13 10:48:07 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm slub: improve bit diffusion for freelist ptr obfuscation 2020-04-13 10:48:07 +02:00
net cfg80211: Do not warn on same channel at the end of CSA 2020-04-17 10:49:59 +02:00
samples samples/bpf: Set -fno-stack-protector when building BPF programs 2020-02-24 08:36:36 +01:00
scripts kconfig: introduce m32-flag and m64-flag 2020-04-08 09:08:37 +02:00
security efi: Only print errors about failing to get certs if EFI vars are found 2020-03-12 13:00:14 +01:00
sound ASoC: jz4740-i2s: Fix divider written at incorrect offset in register 2020-04-13 10:48:09 +02:00
tools selftests/net: add definition for SOL_DCCP to fix compilation errors for old libc 2020-04-17 10:49:59 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:43:48 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 17:22:19 +01:00
Makefile Linux 5.4.32 2020-04-13 10:48:18 +02:00
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.