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tracing: Detect the string nul character when parsing user input string

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User space can pass in a C nul character '\0' along with its input. The
function trace_get_user() will try to process it as a normal character,
and that will fail to parse.

open("/sys/kernel/debug/tracing//set_ftrace_pid", O_WRONLY|O_TRUNC) = 3
write(3, " \0", 2)                      = -1 EINVAL (Invalid argument)

while parse can handle spaces, so below works.

$ echo "" > set_ftrace_pid
$ echo " " > set_ftrace_pid
$ echo -n " " > set_ftrace_pid

Have the parser stop on '\0' and cease any further parsing. Only process
the characters up to the nul '\0' character and do not process it.

Link: http://lkml.kernel.org/r/1516093350-12045-2-git-send-email-changbin.du@intel.com

Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Changbin Du
2018-01-16 17:02:28 +08:00
committed by Steven Rostedt (VMware)
parent 2ee5b92a25
commit 921a7acd85
1 changed files with 3 additions and 3 deletions
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6
kernel/trace/trace.c
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@@ -1237,7 +1237,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
} }
/* only spaces were written */ /* only spaces were written */
if (isspace(ch)) { if (isspace(ch) || !ch) {
*ppos += read; *ppos += read;
ret = read; ret = read;
goto out; goto out;
@@ -1247,7 +1247,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
} }
/* read the non-space input */ /* read the non-space input */
while (cnt && !isspace(ch)) { while (cnt && !isspace(ch) && ch) {
if (parser->idx < parser->size - 1) if (parser->idx < parser->size - 1)
parser->buffer[parser->idx++] = ch; parser->buffer[parser->idx++] = ch;
else { else {
@@ -1262,7 +1262,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
} }
/* We either got finished input or we have to wait for another call. */ /* We either got finished input or we have to wait for another call. */
if (isspace(ch)) { if (isspace(ch) || !ch) {
parser->buffer[parser->idx] = 0; parser->buffer[parser->idx] = 0;
parser->cont = false; parser->cont = false;
} else if (parser->idx < parser->size - 1) { } else if (parser->idx < parser->size - 1) {