Messages in this thread Patch in this message | | | From | Ricardo Neri <> | Subject | [PATCH v11 08/12] x86/umip: Force a page fault when unable to copy emulated result to user | Date | Sun, 5 Nov 2017 18:27:53 -0800 |
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fixup_umip_exception() will be called from do_general_protection(). If the former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV. However, when emulation is successful but the emulated result cannot be copied to user space memory, it is more accurate to issue a SIGSEGV with SEGV_MAPERR with the offending address. A new function, inspired in force_sig_info_fault(), is introduced to model the page fault.
Cc: Andy Lutomirski <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chen Yucong <slaoub@gmail.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tony Luck <tony.luck@intel.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: x86@kernel.org Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- arch/x86/kernel/umip.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 47 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c index d80b816..6ba82be 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -11,6 +11,10 @@ #include <asm/traps.h> #include <asm/insn.h> #include <asm/insn-eval.h> +#include <linux/ratelimit.h> + +#undef pr_fmt +#define pr_fmt(fmt) "umip: " fmt /** DOC: Emulation for User-Mode Instruction Prevention (UMIP) * @@ -196,6 +200,41 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst, } /** + * force_sig_info_umip_fault() - Force a SIGSEGV with SEGV_MAPERR + * @addr: Address that caused the signal + * @regs: Register set containing the instruction pointer + * + * Force a SIGSEGV signal with SEGV_MAPERR as the error code. This function is + * intended to be used to provide a segmentation fault when the result of the + * UMIP emulation could not be copied to the user space memory. + * + * Returns: none + */ +static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs) +{ + siginfo_t info; + struct task_struct *tsk = current; + + tsk->thread.cr2 = (unsigned long)addr; + tsk->thread.error_code = X86_PF_USER | X86_PF_WRITE; + tsk->thread.trap_nr = X86_TRAP_PF; + + info.si_signo = SIGSEGV; + info.si_errno = 0; + info.si_code = SEGV_MAPERR; + info.si_addr = addr; + force_sig_info(SIGSEGV, &info, tsk); + + if (!(show_unhandled_signals && unhandled_signal(tsk, SIGSEGV))) + return; + + pr_err_ratelimited("%s[%d] umip emulation segfault ip:%lx sp:%lx error:%x in %lx\n", + tsk->comm, task_pid_nr(tsk), regs->ip, + regs->sp, X86_PF_USER | X86_PF_WRITE, + regs->ip); +} + +/** * fixup_umip_exception() - Fixup a general protection fault caused by UMIP * @regs: Registers as saved when entering the #GP handler * @@ -311,8 +350,14 @@ bool fixup_umip_exception(struct pt_regs *regs) return false; nr_copied = copy_to_user(uaddr, dummy_data, dummy_data_size); - if (nr_copied > 0) - return false; + if (nr_copied > 0) { + /* + * If copy fails, send a signal and tell caller that + * fault was fixed up. + */ + force_sig_info_umip_fault(uaddr, regs); + return true; + } } /* increase IP to let the program keep going */ -- 2.7.4
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