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criu/log: properly handle truncated length from vsnprintf #2819

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Merged
merged 2 commits into from
Nov 12, 2025
+14 −8
Merged

criu/log: properly handle truncated length from vsnprintf #2819

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cdff770
criu/log: properly handle truncated length from vsnprintf
avagin Nov 11, 2025
2d01694
log: use sizeof(*hdr) instead of sizeof(hdr)
avagin Nov 12, 2025
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22 changes: 14 additions & 8 deletions criu/log.c
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Original file line number Diff line number Diff line change
Expand Up @@ -190,7 +190,7 @@ void flush_early_log_buffer(int fd)
* with reading the log_level.
*/
struct early_log_hdr *hdr = (void *)early_log_buffer + pos;
pos += sizeof(hdr);
pos += sizeof(*hdr);
if (hdr->level <= current_loglevel) {
size_t size = 0;
while (size < hdr->len) {
Expand All @@ -202,7 +202,7 @@ void flush_early_log_buffer(int fd)
}
pos += hdr->len;
}
if (early_log_buf_off == EARLY_LOG_BUF_LEN)
if ((early_log_buf_off + sizeof(struct early_log_hdr)) >= EARLY_LOG_BUF_LEN)
pr_warn("The early log buffer is full, some messages may have been lost\n");
early_log_buf_off = 0;
}
Expand Down Expand Up @@ -320,31 +320,37 @@ unsigned int log_get_loglevel(void)

static void early_vprint(const char *format, unsigned int loglevel, va_list params)
{
unsigned int log_size = 0;
int log_size = 0, log_space;
struct early_log_hdr *hdr;

if ((early_log_buf_off + sizeof(hdr)) >= EARLY_LOG_BUF_LEN)
if ((early_log_buf_off + sizeof(*hdr)) >= EARLY_LOG_BUF_LEN)
return;

/* Save loglevel */

hdr = (void *)early_log_buffer + early_log_buf_off;
hdr->level = loglevel;
/* Skip the log entry size */
early_log_buf_off += sizeof(hdr);
early_log_buf_off += sizeof(*hdr);
log_space = EARLY_LOG_BUF_LEN - early_log_buf_off;
if (loglevel >= LOG_TIMESTAMP) {
/*
* If logging is not yet setup we just write zeros
* instead of a real timestamp. This way we can
* keep the same format as the other messages on
* log levels with timestamps (>=LOG_TIMESTAMP).
*/
log_size = snprintf(early_log_buffer + early_log_buf_off, sizeof(early_log_buffer) - early_log_buf_off,
log_size = snprintf(early_log_buffer + early_log_buf_off, log_space,
"(00.000000) ");
}

log_size += vsnprintf(early_log_buffer + early_log_buf_off + log_size,
sizeof(early_log_buffer) - early_log_buf_off - log_size, format, params);
if (log_size < log_space)
log_size += vsnprintf(early_log_buffer + early_log_buf_off + log_size,
log_space - log_size, format, params);
if (log_size > log_space) {
/* vsnprintf always add the terminating null byte. */
log_size = log_space - 1;
}

/* Save log entry size */
hdr->len = log_size;
Expand Down
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