@@ -269,14 +269,19 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
long do_syscall_trace_enter(struct pt_regs *regs)
{
- long ret = 0;
-
/* Do the secure computing check first. */
secure_computing_strict(regs->gr[20]);
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
- ret = -1L;
+ tracehook_report_syscall_entry(regs)) {
+ /*
+ * Tracing decided this syscall should not happen or the
+ * debugger stored an invalid system call number. Skip
+ * the system call and the system call restart handling.
+ */
+ regs->gr[20] = -1UL;
+ goto out;
+ }
#ifdef CONFIG_64BIT
if (!is_compat_task())
@@ -290,7 +295,8 @@ long do_syscall_trace_enter(struct pt_regs *regs)
regs->gr[24] & 0xffffffff,
regs->gr[23] & 0xffffffff);
- return ret ? : regs->gr[20];
+out:
+ return regs->gr[20];
}
void do_syscall_trace_exit(struct pt_regs *regs)
@@ -343,7 +343,7 @@ tracesys_next:
#endif
comiclr,>>= __NR_Linux_syscalls, %r20, %r0
- b,n .Lsyscall_nosys
+ b,n .Ltracesys_nosys
LDREGX %r20(%r19), %r19
@@ -359,6 +359,9 @@ tracesys_next:
be 0(%sr7,%r19)
ldo R%tracesys_exit(%r2),%r2
+.Ltracesys_nosys:
+ ldo -ENOSYS(%r0),%r28 /* set errno */
+
/* Do *not* call this function on the gateway page, because it
makes a direct call to syscall_trace. */
This is a note to let you know that I have just added a patch titled parisc: Fix ptrace syscall number and return value modification to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue This patch is scheduled to be released in version 4.2.8-ckt6. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 4.2.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 09c7d23bba14026e60d09d970938bd92d20cd39e Mon Sep 17 00:00:00 2001 From: Helge Deller <deller@gmx.de> Date: Tue, 19 Jan 2016 16:08:49 +0100 Subject: parisc: Fix ptrace syscall number and return value modification commit 98e8b6c9ac9d1b1e9d1122dfa6783d5d566bb8f7 upstream. Mike Frysinger reported that his ptrace testcase showed strange behaviour on parisc: It was not possible to avoid a syscall and the return value of a syscall couldn't be changed. To modify a syscall number, we were missing to save the new syscall number to gr20 which is then picked up later in assembly again. The effect that the return value couldn't be changed is a side-effect of another bug in the assembly code. When a process is ptraced, userspace expects each syscall to report entrance and exit of a syscall. If a syscall number was given which doesn't exist, we jumped to the normal syscall exit code instead of informing userspace that the (non-existant) syscall exits. This unexpected behaviour confuses userspace and thus the bug was misinterpreted as if we can't change the return value. This patch fixes both problems and was tested on 64bit kernel with 32bit userspace. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Mike Frysinger <vapier@gentoo.org> Tested-by: Mike Frysinger <vapier@gentoo.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/parisc/kernel/ptrace.c | 16 +++++++++++----- arch/parisc/kernel/syscall.S | 5 ++++- 2 files changed, 15 insertions(+), 6 deletions(-) -- 2.7.0