mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-06 10:58:48 +09:00
c730fce7c7
Thomas Richter reported a crash in linux-next with a backtrace similar
to the following one:
[<0000000000000000>] 0x0
([<000000000031a182>] bpf_trace_run4+0xc2/0x218)
[<00000000001d59f4>] __bpf_trace_sched_switch+0x1c/0x28
[<0000000000c44a3a>] __schedule+0x43a/0x890
[<0000000000c44ef8>] schedule+0x68/0x110
[<0000000000c4e5ca>] do_nanosleep+0xa2/0x168
[<000000000026e7fe>] hrtimer_nanosleep+0xf6/0x1c0
[<000000000026eb6e>] __s390x_sys_nanosleep+0xb6/0xf0
[<0000000000c3b81c>] __do_syscall+0x1e4/0x208
[<0000000000c50510>] system_call+0x70/0x98
Last Breaking-Event-Address:
[<000003ff7fda1814>] bpf_prog_65e887c70a835bbf_on_switch+0x1a4/0x1f0
The problem is that bpf_arch_text_poke() with new_addr == NULL is
susceptible to the following race condition:
T1 T2
----------------- -------------------
plt.target = NULL
entry: brcl 0xf,plt
entry.mask = 0
lgrl %r1,plt.target
br %r1
Fix by setting PLT target to the instruction following `brcl 0xf,plt`
instead of 0. This way T2 will simply resume the execution of the eBPF
program, which is the desired effect of passing new_addr == NULL.
Fixes: f1d5df84cd ("s390/bpf: Implement bpf_arch_text_poke()")
Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20230414154755.184502-1-iii@linux.ibm.com
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.