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Filename Latest commit message Latest commit date
Johannes Berg 2fe3fbcc53 um: Mark all kernel symbols as local
[ Upstream commit d5027ca63e0e778b641cf23e3f5c6d6212cf412b ]

Ritesh reported a bug [1] against UML, noting that it crashed on
startup. The backtrace shows the following (heavily redacted):

(gdb) bt
...
 #26 0x0000000060015b5d in sem_init () at ipc/sem.c:268
 #27 0x00007f89906d92f7 in ?? () from /lib/x86_64-linux-gnu/libcom_err.so.2
 #28 0x00007f8990ab8fb2 in call_init (...) at dl-init.c:72
...
 #40 0x00007f89909bf3a6 in nss_load_library (...) at nsswitch.c:359
...
 #44 0x00007f8990895e35 in _nss_compat_getgrnam_r (...) at nss_compat/compat-grp.c:486
 #45 0x00007f8990968b85 in __getgrnam_r [...]
 #46 0x00007f89909d6b77 in grantpt [...]
 #47 0x00007f8990a9394e in __GI_openpty [...]
 #48 0x00000000604a1f65 in openpty_cb (...) at arch/um/os-Linux/sigio.c:407
 #49 0x00000000604a58d0 in start_idle_thread (...) at arch/um/os-Linux/skas/process.c:598
 #50 0x0000000060004a3d in start_uml () at arch/um/kernel/skas/process.c:45
 #51 0x00000000600047b2 in linux_main (...) at arch/um/kernel/um_arch.c:334
 #52 0x000000006000574f in main (...) at arch/um/os-Linux/main.c:144

indicating that the UML function openpty_cb() calls openpty(),
which internally calls __getgrnam_r(), which causes the nsswitch
machinery to get started.

This loads, through lots of indirection that I snipped, the
libcom_err.so.2 library, which (in an unknown function, "??")
calls sem_init().

Now, of course it wants to get libpthread's sem_init(), since
it's linked against libpthread. However, the dynamic linker
looks up that symbol against the binary first, and gets the
kernel's sem_init().

Hajime Tazaki noted that "objcopy -L" can localize a symbol,
so the dynamic linker wouldn't do the lookup this way. I tried,
but for some reason that didn't seem to work.

Doing the same thing in the linker script instead does seem to
work, though I cannot entirely explain - it *also* works if I
just add "VERSION { { global: *; }; }" instead, indicating that
something else is happening that I don't really understand. It
may be that explicitly doing that marks them with some kind of
empty version, and that's different from the default.

Explicitly marking them with a version breaks kallsyms, so that
doesn't seem to be possible.

Marking all the symbols as local seems correct, and does seem
to address the issue, so do that. Also do it for static link,
nsswitch libraries could still be loaded there.

[1] https://bugs.debian.org/983379

Reported-by: Ritesh Raj Sarraf <rrs@debian.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Tested-By: Ritesh Raj Sarraf <rrs@debian.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-05-22 11:38:28 +02:00
arch um: Mark all kernel symbols as local 2021-05-22 11:38:28 +02:00
block blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-19 10:08:30 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 10:26:29 +01:00
crypto crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS 2021-05-11 14:04:15 +02:00
Documentation ARM: 9012/1: move device tree mapping out of linear region 2021-05-19 10:08:32 +02:00
drivers Input: silead - add workaround for x86 BIOS-es which bring the chip up in a stuck state 2021-05-22 11:38:28 +02:00
fs f2fs: fix error handling in f2fs_end_enable_verity() 2021-05-19 10:08:32 +02:00
include virtio_net: Do not pull payload in skb->head 2021-05-22 11:38:28 +02:00
init init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM 2021-04-10 13:34:32 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel kernel: kexec_file: fix error return code of kexec_calculate_store_digests() 2021-05-19 10:08:28 +02:00
lib kobject_uevent: remove warning in init_uevent_argv() 2021-05-19 10:08:33 +02:00
LICENSES
mm mm/hugetlb: fix F_SEAL_FUTURE_WRITE 2021-05-19 10:08:29 +02:00
net xsk: Simplify detection of empty and full rings 2021-05-22 11:38:27 +02:00
samples samples/bpf: Fix broken tracex1 due to kprobe argument change 2021-05-19 10:08:23 +02:00
scripts kconfig: nconf: stop endless search loops 2021-05-19 10:08:23 +02:00
security security: commoncap: fix -Wstringop-overread warning 2021-05-11 14:04:16 +02:00
sound ASoC: rsnd: check all BUSIF status when error 2021-05-19 10:08:33 +02:00
tools selftests: Set CC to clang in lib.mk if LLVM is set 2021-05-19 10:08:22 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: Stop looking for coalesced MMIO zones if the bus is destroyed 2021-05-14 09:44:15 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.120 2021-05-19 10:08:33 +02:00
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.