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journal-upload: add asserts that snprintf does not return an error

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LGMT complains:
> The size argument of this snprintf call is derived from its return value,
> which may exceed the size of the buffer and overflow.

Let's make sure that r is non-negative. (This shouldn't occur unless the format
string is borked, so let's just add an assert.)
Then, let's reorder the comparison to avoid the potential overflow.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2018-10-02 12:46:31 +02:00
parent 7c3733d5de
commit 91db8ed5b2
1 changed files with 8 additions and 4 deletions
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12
src/journal-remote/journal-upload-journal.c
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@ -34,7 +34,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
r = snprintf(buf + pos, size - pos,
"__CURSOR=%s\n", u->current_cursor);
if (pos + r > size)
assert(r >= 0);
if ((size_t) r > size - pos)
/* not enough space */
return pos;
@ -58,7 +59,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
r = snprintf(buf + pos, size - pos,
"__REALTIME_TIMESTAMP="USEC_FMT"\n", realtime);
if (r + pos > size)
assert(r >= 0);
if ((size_t) r > size - pos)
/* not enough space */
return pos;
@ -83,7 +85,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
r = snprintf(buf + pos, size - pos,
"__MONOTONIC_TIMESTAMP="USEC_FMT"\n", monotonic);
if (r + pos > size)
assert(r >= 0);
if ((size_t) r > size - pos)
/* not enough space */
return pos;
@ -108,7 +111,8 @@ static ssize_t write_entry(char *buf, size_t size, Uploader *u) {
r = snprintf(buf + pos, size - pos,
"_BOOT_ID=%s\n", sd_id128_to_string(boot_id, sid));
if (r + pos > size)
assert(r >= 0);
if ((size_t) r > size - pos)
/* not enough space */
return pos;