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| author | Gerald Schaefer <gerald.schaefer@de.ibm.com> | 2010-05-12 09:32:12 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-05-26 14:32:06 -0700 |
| commit | 6304f31cfc670abcd2006c18cf8d960072c00c5c (patch) | |
| tree | 960466726613074c735c5e6eb2c71360174dd65c | |
| parent | d53662168530910feb44e0058b10e9b4ec2302be (diff) | |
| download | lwn-6304f31cfc670abcd2006c18cf8d960072c00c5c.tar.gz lwn-6304f31cfc670abcd2006c18cf8d960072c00c5c.zip | |
ptrace: fix return value of do_syscall_trace_enter()
commit 545c174d1f093a462b4bb9131b23d5ea72a600e1 upstream.
strace may change the system call number, so regs->gprs[2] must not
be read before tracehook_report_syscall_entry(). This fixes a bug
where "strace -f" will hang after a vfork().
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | arch/s390/kernel/ptrace.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c index 7cf464234419..11e94de973ad 100644 --- a/arch/s390/kernel/ptrace.c +++ b/arch/s390/kernel/ptrace.c @@ -640,7 +640,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request, asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) { - long ret; + long ret = 0; /* Do the secure computing check first. */ secure_computing(regs->gprs[2]); @@ -649,7 +649,6 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) * The sysc_tracesys code in entry.S stored the system * call number to gprs[2]. */ - ret = regs->gprs[2]; if (test_thread_flag(TIF_SYSCALL_TRACE) && (tracehook_report_syscall_entry(regs) || regs->gprs[2] >= NR_syscalls)) { @@ -671,7 +670,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) regs->gprs[2], regs->orig_gpr2, regs->gprs[3], regs->gprs[4], regs->gprs[5]); - return ret; + return ret ?: regs->gprs[2]; } asmlinkage void do_syscall_trace_exit(struct pt_regs *regs) |