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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2021-05-13 19:23:24 +0300
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2021-05-13 21:20:33 +0300
commiteb01f5353bdaa59600b29d864819056a0e3de24d (patch)
tree6b461e8d593c507df90d3484a6c5a302d1cdc1b5
parent6efb943b8616ec53a5e444193dccf1af9ad627b5 (diff)
downloadlinux-eb01f5353bdaa59600b29d864819056a0e3de24d.tar.xz
tracing: Handle %.*s in trace_check_vprintf()
If a trace event uses the %*.s notation, the trace_check_vprintf() will fail and will warn about a bad processing of strings, because it does not take into account the length field when processing the star (*) part. Have it handle this case as well. Link: https://lore.kernel.org/linux-nfs/238C0E2D-C2A4-4578-ADD2-C565B3B99842@oracle.com/ Reported-by: Chuck Lever III <chuck.lever@oracle.com> Fixes: 9a6944fee68e2 ("tracing: Add a verifier to check string pointers for trace events") Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-rw-r--r--kernel/trace/trace.c31
1 files changed, 27 insertions, 4 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 560e4c8d3825..a21ef9cd2aae 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3704,6 +3704,9 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
goto print;
while (*p) {
+ bool star = false;
+ int len = 0;
+
j = 0;
/* We only care about %s and variants */
@@ -3725,13 +3728,17 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
/* Need to test cases like %08.*s */
for (j = 1; p[i+j]; j++) {
if (isdigit(p[i+j]) ||
- p[i+j] == '*' ||
p[i+j] == '.')
continue;
+ if (p[i+j] == '*') {
+ star = true;
+ continue;
+ }
break;
}
if (p[i+j] == 's')
break;
+ star = false;
}
j = 0;
}
@@ -3744,6 +3751,9 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
iter->fmt[i] = '\0';
trace_seq_vprintf(&iter->seq, iter->fmt, ap);
+ if (star)
+ len = va_arg(ap, int);
+
/* The ap now points to the string data of the %s */
str = va_arg(ap, const char *);
@@ -3762,8 +3772,18 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
int ret;
/* Try to safely read the string */
- ret = strncpy_from_kernel_nofault(iter->fmt, str,
- iter->fmt_size);
+ if (star) {
+ if (len + 1 > iter->fmt_size)
+ len = iter->fmt_size - 1;
+ if (len < 0)
+ len = 0;
+ ret = copy_from_kernel_nofault(iter->fmt, str, len);
+ iter->fmt[len] = 0;
+ star = false;
+ } else {
+ ret = strncpy_from_kernel_nofault(iter->fmt, str,
+ iter->fmt_size);
+ }
if (ret < 0)
trace_seq_printf(&iter->seq, "(0x%px)", str);
else
@@ -3775,7 +3795,10 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
strncpy(iter->fmt, p + i, j + 1);
iter->fmt[j+1] = '\0';
}
- trace_seq_printf(&iter->seq, iter->fmt, str);
+ if (star)
+ trace_seq_printf(&iter->seq, iter->fmt, len, str);
+ else
+ trace_seq_printf(&iter->seq, iter->fmt, str);
p += i + j + 1;
}