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semihosting: Fix handling of buffer in TARGET_SYS_TMPNAM

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The TARGET_SYS_TMPNAM implementation has two bugs spotted by
Coverity:
 * confusion about whether 'len' has the length of the string
   including or excluding the terminating NUL means we
   lock_user() len bytes of memory but memcpy() len + 1 bytes
 * In the error-exit cases we forget to free() the buffer
   that asprintf() returned to us

Resolves: Coverity CID 1490285, 1490289
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220719121110.225657-5-peter.maydell@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220725140520.515340-10-alex.bennee@linaro.org>
This commit is contained in:
Peter Maydell 2022-07-25 15:05:16 +01:00 committed by Alex Bennée
parent fed49cdf6a
commit 9b1268f55c
1 changed files with 11 additions and 2 deletions
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13
semihosting/arm-compat-semi.c
View file

@ -504,16 +504,25 @@ void do_common_semihosting(CPUState *cs)
GET_ARG(1);
GET_ARG(2);
len = asprintf(&s, "/tmp/qemu-%x%02x", getpid(), (int)arg1 & 0xff);
if (len < 0) {
common_semi_set_ret(cs, -1);
break;
}
/* Allow for trailing NUL */
len++;
/* Make sure there's enough space in the buffer */
if (len < 0 || len >= arg2) {
if (len > arg2) {
free(s);
common_semi_set_ret(cs, -1);
break;
}
p = lock_user(VERIFY_WRITE, arg0, len, 0);
if (!p) {
free(s);
goto do_fault;
}
memcpy(p, s, len + 1);
memcpy(p, s, len);
unlock_user(p, arg0, len);
free(s);
common_semi_set_ret(cs, 0);