add manually reviewed semantic bugs

1 files changed, 71 insertions, 0 deletions

diff --git a/results/classifier/semantic-bugs/instruction/1824344 b/results/classifier/semantic-bugs/instruction/1824344
new file mode 100644
index 000000000..9886d36a4
--- /dev/null
+++ b/results/classifier/semantic-bugs/instruction/1824344
@@ -0,0 +1,71 @@
+instruction: 0.928
+assembly: 0.842
+device: 0.543
+semantic: 0.396
+network: 0.367
+socket: 0.356
+other: 0.327
+boot: 0.303
+vnc: 0.251
+graphic: 0.236
+mistranslation: 0.196
+KVM: 0.008
+
+x86: retf or iret pagefault sets wrong error code
+
+With a x86_64 or i386 guest, non-KVM, when trying to execute a
+"iret/iretq/retf" instruction in userspace with invalid stack pointer
+(under a protected mode OS, like Linux), wrong bits are set in the
+pushed error code; bit 2 is not set, indicating the error comes from
+kernel space.
+
+If the guest OS is using this flag to decide whether this was a kernel
+or user page fault, it will mistakenly decide a kernel has irrecoverably
+faulted, possibly causing guest OS panic.
+
+
+How to reproduce the problem a guest (non-KVM) Linux:
+Note, on recent Linux kernel version, this needs a CPU with SMAP support
+(eg. -cpu max)
+
+$ cat tst.c
+int main()
+{
+__asm__ volatile (
+"mov $0,%esp\n"
+"retf"
+);
+return 0;
+}
+
+$ gcc tst.c
+$ ./a.out
+Killed
+
+
+"dmesg" shows the kernel has in fact triggered a "BUG: unable to handle
+kernel NULL pointer dereference...", but it has "recovered" by killing
+the faulting process (see attached screenshot).
+
+
+Using self-compiled qemu from git:
+commit 532cc6da74ec25b5ba6893b5757c977d54582949 (HEAD -> master, tag: v4.0.0-rc3, origin/master, origin/HEAD)
+Author: Peter Maydell <email address hidden>
+Date:   Wed Apr 10 15:38:59 2019 +0100
+
+    Update version for v4.0.0-rc3 release
+    
+    Signed-off-by: Peter Maydell <email address hidden>
+
+
+
+This appears to be similar to https://bugs.launchpad.net/qemu/+bug/1866892 (and much simpler)
+
+
+This is an automated cleanup. This bug report has been moved to QEMU's
+new bug tracker on gitlab.com and thus gets marked as 'expired' now.
+Please continue with the discussion here:
+
+ https://gitlab.com/qemu-project/qemu/-/issues/265
+
+