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35e3815fa8
The recursion check in __bpf_prog_enter and __bpf_prog_exit
leaves some (not inlined) functions unprotected:
In __bpf_prog_enter:
- migrate_disable is called before prog->active is checked
In __bpf_prog_exit:
- migrate_enable,rcu_read_unlock_strict are called after
prog->active is decreased
When attaching trampoline to them we get panic like:
traps: PANIC: double fault, error_code: 0x0
double fault: 0000 [#1] SMP PTI
RIP: 0010:__bpf_prog_enter+0x4/0x50
...
Call Trace:
<IRQ>
bpf_trampoline_6442466513_0+0x18/0x1000
migrate_disable+0x5/0x50
__bpf_prog_enter+0x9/0x50
bpf_trampoline_6442466513_0+0x18/0x1000
migrate_disable+0x5/0x50
__bpf_prog_enter+0x9/0x50
bpf_trampoline_6442466513_0+0x18/0x1000
migrate_disable+0x5/0x50
__bpf_prog_enter+0x9/0x50
bpf_trampoline_6442466513_0+0x18/0x1000
migrate_disable+0x5/0x50
...
Fixing this by adding deny list of btf ids for tracing
programs and checking btf id during program verification.
Adding above functions to this list.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210429114712.43783-1-jolsa@kernel.org
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.