@@ -170,6 +170,7 @@ int ptrace_setfpregs(struct task_struct *child, __u32 __user *data)
__get_user(fregs[i], i + (__u64 __user *) data);
__get_user(child->thread.fpu.fcr31, data + 64);
+ child->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X;
/* FIR may not be written. */
@@ -587,7 +588,7 @@ long arch_ptrace(struct task_struct *child, long request,
break;
#endif
case FPC_CSR:
- child->thread.fpu.fcr31 = data;
+ child->thread.fpu.fcr31 = data & ~FPU_CSR_ALL_X;
break;
case DSP_BASE ... DSP_BASE + 5: {
dspreg_t *dregs;
This is a note to let you know that I have just added a patch titled MIPS: Prevent user from setting FCSR cause bits to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11.7. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 128362f3def646603e4d1b92ea03af22e3febc60 Mon Sep 17 00:00:00 2001 From: Paul Burton <paul.burton@imgtec.com> Date: Tue, 22 Jul 2014 14:21:21 +0100 Subject: MIPS: Prevent user from setting FCSR cause bits commit b1442d39fac2fcfbe6a4814979020e993ca59c9e upstream. If one or more matching FCSR cause & enable bits are set in saved thread context then when that context is restored the kernel will take an FP exception. This is of course undesirable and considered an oops, leading to the kernel writing a backtrace to the console and potentially rebooting depending upon the configuration. Thus the kernel avoids this situation by clearing the cause bits of the FCSR register when handling FP exceptions and after emulating FP instructions. However the kernel does not prevent userland from setting arbitrary FCSR cause & enable bits via ptrace, using either the PTRACE_POKEUSR or PTRACE_SETFPREGS requests. This means userland can trivially cause the kernel to oops on any system with an FPU. Prevent this from happening by clearing the cause bits when writing to the saved FCSR context via ptrace. This problem appears to exist at least back to the beginning of the git era in the PTRACE_POKEUSR case. Signed-off-by: Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Cc: Paul Burton <paul.burton@imgtec.com> Patchwork: https://patchwork.linux-mips.org/patch/7438/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/mips/kernel/ptrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) -- 1.9.1