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author | Oleg Nesterov <oleg@redhat.com> | 2020-07-23 17:44:20 +0200 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-07-29 10:18:29 +0200 |
commit | ee2f6a6b39be3284c57f0c22f026ade9160fdf57 (patch) | |
tree | eddbe7cbe81ce5b395c01870584ead0cb89bf8b0 /kernel | |
parent | ee08663380ffd5a45a1c87580fbc305e8413c235 (diff) | |
download | linux-stable-ee2f6a6b39be3284c57f0c22f026ade9160fdf57.tar.gz linux-stable-ee2f6a6b39be3284c57f0c22f026ade9160fdf57.tar.bz2 linux-stable-ee2f6a6b39be3284c57f0c22f026ade9160fdf57.zip |
uprobes: Change handle_swbp() to send SIGTRAP with si_code=SI_KERNEL, to fix GDB regression
commit fe5ed7ab99c656bd2f5b79b49df0e9ebf2cead8a upstream.
If a tracee is uprobed and it hits int3 inserted by debugger, handle_swbp()
does send_sig(SIGTRAP, current, 0) which means si_code == SI_USER. This used
to work when this code was written, but then GDB started to validate si_code
and now it simply can't use breakpoints if the tracee has an active uprobe:
# cat test.c
void unused_func(void)
{
}
int main(void)
{
return 0;
}
# gcc -g test.c -o test
# perf probe -x ./test -a unused_func
# perf record -e probe_test:unused_func gdb ./test -ex run
GNU gdb (GDB) 10.0.50.20200714-git
...
Program received signal SIGTRAP, Trace/breakpoint trap.
0x00007ffff7ddf909 in dl_main () from /lib64/ld-linux-x86-64.so.2
(gdb)
The tracee hits the internal breakpoint inserted by GDB to monitor shared
library events but GDB misinterprets this SIGTRAP and reports a signal.
Change handle_swbp() to use force_sig(SIGTRAP), this matches do_int3_user()
and fixes the problem.
This is the minimal fix for -stable, arch/x86/kernel/uprobes.c is equally
wrong; it should use send_sigtrap(TRAP_TRACE) instead of send_sig(SIGTRAP),
but this doesn't confuse GDB and needs another x86-specific patch.
Reported-by: Aaron Merey <amerey@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200723154420.GA32043@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/events/uprobes.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 291680ba8504..aa83538efc23 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2205,7 +2205,7 @@ static void handle_swbp(struct pt_regs *regs) if (!uprobe) { if (is_swbp > 0) { /* No matching uprobe; signal SIGTRAP. */ - send_sig(SIGTRAP, current, 0); + force_sig(SIGTRAP); } else { /* * Either we raced with uprobe_unregister() or we can't |