RFR: 8296812: sprintf is deprecated in Xcode 14 [v7]

[Thomas Stuefe]

On Wed, 16 Nov 2022 07:03:12 GMT, Xue-Lei Andrew Fan <xuelei at openjdk.org> wrote:

>> Hi,
>> 
>> May I have this update reviewed?
>> 
>> The sprintf is deprecated in Xcode 14 because of security concerns, and the use of it causing building failure.  The build could pass if warnings are disabled for codes that use sprintf method.  For the long run, the sprintf could be replaced with snprintf.  This patch is trying to check if snprintf could be used.
>> 
>> Thanks,
>> Xuelei
>
> Xue-Lei Andrew Fan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   address review comments

src/hotspot/os/bsd/attachListener_bsd.cpp line 295:

> 293:             char msg[32];
> 294:             int msg_len = os::snprintf(msg, sizeof(msg), "%d\n", ATTACH_ERROR_BADVERSION);
> 295:             write_fully(s, msg, msg_len);

Assuming C99 behavior: safe but only because the buffer is large enough ("%d\n" needs at most 12 bytes, buffer is 32). Were it to overflow, msg_len would be larger than sizeof(msg) and we would probably end up reading beyond the message end in write_fully. So not really better than using sprintf+strlen.

src/hotspot/os/bsd/attachListener_bsd.cpp line 415:

> 413:   char msg[32];
> 414:   int msg_len = os::snprintf(msg, sizeof(msg), "%d\n", result);
> 415:   int rc = BsdAttachListener::write_fully(this->socket(), msg, msg_len);

same

src/hotspot/share/adlc/output_c.cpp line 217:

> 215:     const PipeClassOperandForm *tmppipeopnd =
> 216:         (const PipeClassOperandForm *)pipeclass->_localUsage[paramname];
> 217:     templen += snprintf(&operand_stages[templen], operand_stages_size - templen, "  stage_%s%c\n",

C99 Behavior: all these are probably safe but only because we never overstepped the buffer in the first place, the buffer size is pre-calculated. If it is incorrect and we have a truncation, subsequent writes will write beyond the buffer.

src/hotspot/share/classfile/javaClasses.cpp line 2527:

> 2525: 
> 2526:   // Print stack trace line in buffer
> 2527:   size_t buf_off = os::snprintf(buf, buf_size, "\tat %s.%s(", klass_name, method_name);

Here, and in subsequent uses: assuming C99 behavior of snprintf, if we truncated in snprintf, buf_off will be > buffer size, (buf + buf_off) point beyond the buffer, (buf_size - buf_off) will overflow and become very large.

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PR: https://git.openjdk.org/jdk/pull/11115