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parasite: don't block SIGTRAP

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This is the workaround for #1429.

The parasite code contains instructions that trigger SIGTRAP to stop at
certain points. In such cases, the kernel sends a force SIGTRAP that
can't be ignore and if it is blocked, the kernel resets its signal
handler to a default one and unblocks it. It means that if we want to
save the origin signal handle

Signed-off-by: Andrei Vagin <avagin@gmail.com>
This commit is contained in:
Andrei Vagin
2021-05-20 19:32:53 +03:00
parent ed58fb2214
commit 61c7cc5a92
2 changed files with 24 additions and 0 deletions
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6
compel/include/uapi/ksigset.h
View File

@@ -22,4 +22,10 @@ static inline void ksigaddset(k_rtsigset_t *set, int _sig)
int sig = _sig - 1;
set->sig[sig / _NSIG_BPW] |= 1UL << (sig % _NSIG_BPW);
}
static inline void ksigdelset(k_rtsigset_t *set, int _sig)
{
int sig = _sig - 1;
set->sig[sig / _NSIG_BPW] |= ~(1UL << (sig % _NSIG_BPW));
}
#endif

18
compel/src/lib/infect.c
View File

@@ -281,6 +281,19 @@ try_again:
if (ss->seccomp_mode != SECCOMP_MODE_DISABLED && ptrace_suspend_seccomp(pid) < 0)
goto err;
/*
* FIXME(issues/1429): parasite code contains instructions that trigger
* SIGTRAP to stop at certain points. In such cases, the kernel sends a
* force SIGTRAP that can't be ignored and if it is blocked, the kernel
* resets its signal handler to a default one and unblocks it. It means
* that if we want to save the origin signal handler, we need to run a
* parasite code with the unblocked SIGTRAP.
*/
if ((ss->sigpnd | ss->shdpnd) & (1 << (SIGTRAP - 1))) {
pr_err("Can't dump the %d thread with a pending SIGTRAP.\n", pid);
goto err;
}
nr_sigstop = 0;
if (ss->sigpnd & (1 << (SIGSTOP - 1)))
nr_sigstop++;
@@ -447,6 +460,11 @@ static int parasite_run(pid_t pid, int cmd, unsigned long ip, void *stack,
k_rtsigset_t block;
ksigfillset(&block);
/*
* FIXME(issues/1429): SIGTRAP can't be blocked, otherwice its hanlder
* will be reseted to the default one.
*/
ksigdelset(&block, SIGTRAP);
if (ptrace(PTRACE_SETSIGMASK, pid, sizeof(k_rtsigset_t), &block)) {
pr_perror("Can't block signals for %d", pid);
goto err_sig;