[PATCH] target/mips: Handle lock_user() failure in UHI_plog semihosting call

[Peter Maydell]

Coverity notes that we forgot to check the error return from
lock_user() in one place in the handling of the UHI_plog semihosting
call.  Add the missing error handling.
report_fault() is rather brutal in that it will call abort(), but
this is the same error-handling used in the rest of this file.

Resolves: Coverity CID 1490684
Fixes: ea4210600db3c5 ("target/mips: Avoid qemu_semihosting_log_out for 
UHI_plog")
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
NB: only tested with 'make check' and 'make check-tcg', which
almost certainly don't actually exercise this codepath.
---
 target/mips/tcg/sysemu/mips-semi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/target/mips/tcg/sysemu/mips-semi.c 
b/target/mips/tcg/sysemu/mips-semi.c
index 5fb1ad90920..85f0567a7fa 100644
--- a/target/mips/tcg/sysemu/mips-semi.c
+++ b/target/mips/tcg/sysemu/mips-semi.c
@@ -321,6 +321,9 @@ void mips_semihosting(CPUMIPSState *env)
             if (use_gdb_syscalls()) {
                 addr = gpr[29] - str->len;
                 p = lock_user(VERIFY_WRITE, addr, str->len, 0);
+                if (!p) {
+                    report_fault(env);
+                }
                 memcpy(p, str->str, str->len);
                 unlock_user(p, addr, str->len);
                 semihost_sys_write(cs, uhi_cb, 2, addr, str->len);
-- 
2.25.1