x86/insn-eval: Make 0 a valid RIP for insn_get_effective_ip()

In theory, 0 is a valid value for the instruction pointer so don't use
it as the error return value from insn_get_effective_ip().

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210614135327.9921-5-joro@8bytes.org

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index a67afd7..4eecb9c 100644 (file)
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -1417,7 +1417,7 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
        }
 }
 
-static unsigned long insn_get_effective_ip(struct pt_regs *regs)
+static int insn_get_effective_ip(struct pt_regs *regs, unsigned long *ip)
 {
        unsigned long seg_base = 0;
 
@@ -1430,10 +1430,12 @@ static unsigned long insn_get_effective_ip(struct pt_regs *regs)
        if (!user_64bit_mode(regs)) {
                seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS);
                if (seg_base == -1L)
-                       return 0;
+                       return -EINVAL;
        }
 
-       return seg_base + regs->ip;
+       *ip = seg_base + regs->ip;
+
+       return 0;
 }
 
 /**
@@ -1455,8 +1457,7 @@ int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
        unsigned long ip;
        int not_copied;
 
-       ip = insn_get_effective_ip(regs);
-       if (!ip)
+       if (insn_get_effective_ip(regs, &ip))
                return 0;
 
        not_copied = copy_from_user(buf, (void __user *)ip, MAX_INSN_SIZE);
@@ -1484,8 +1485,7 @@ int insn_fetch_from_user_inatomic(struct pt_regs *regs, unsigned char buf[MAX_IN
        unsigned long ip;
        int not_copied;
 
-       ip = insn_get_effective_ip(regs);
-       if (!ip)
+       if (insn_get_effective_ip(regs, &ip))
                return 0;
 
        not_copied = __copy_from_user_inatomic(buf, (void __user *)ip, MAX_INSN_SIZE);