dtc: Ensure #line directives don't consume data from the next line

Commit Message

Stephen Warren May 31, 2013, 5:14 p.m. UTC

From: Stephen Warren <[e-mail]>

Previously, the #line parsing regex ended with ({WS}+[0-9]+)?. The {WS}
could match line-break characters. If the #line directive did not contain
the optional flags field at the end, this could cause any integer data on
the next line to be consumed as part of the #line directive parsing. This
could cause syntax errors (i.e. #line parsing consuming the leading 0
from a hex constant 0x1234, leaving x1234 to be parsed as cell data,
which is a syntax error), or invalid compilation results (i.e. simply
consuming integer 1234 as part of the #line processing, thus removing it
from the cell data).

Fix this by replacing {WS} with [ \t] so that it can't match line-breaks.

Reported-by: Ian Campbell <[e-mail]>
Signed-off-by: Stephen Warren <[e-mail]>
---
This is a patch for dtc upstream, in response to thread "DTB build
failure due to preproccessing". If/when it's accepted into dtc, I'll
follow up with a kernel patch that makes the same fix.

 dtc-lexer.l               |    2 +-
 tests/line_directives.dts |   10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

Comments

Andreas Schwab May 31, 2013, 5:38 p.m. UTC | #1

Stephen Warren <[e-mail]> writes:

> Fix this by replacing {WS} with [ \t] so that it can't match line-breaks.

I think the other uses of {WS} shouldn't span lines either.

Andreas.

Stephen Warren May 31, 2013, 5:42 p.m. UTC | #2

On 05/31/2013 11:38 AM, Andreas Schwab wrote:
> Stephen Warren <[e-mail]> writes:
> 
>> Fix this by replacing {WS} with [ \t] so that it can't match line-breaks.
> 
> I think the other uses of {WS} shouldn't span lines either.

That is true, but only the optional occurrence /should/ matter. Any
changes to the other occurrences would only affect malformed #line
directives, whereas changing this one occurrence would also affect
well-formed #line directives, due to the optional nature of the trailing
flags field.

Still, it may be reasonable just to change all the occurrences anyway.
Does anyone have a strong opinion either way?
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Patch

diff --git a/dtc-lexer.l b/dtc-lexer.l
index 254d5af..a3a4c69 100644
--- a/dtc-lexer.l
+++ b/dtc-lexer.l
@@ -71,7 +71,7 @@  static int pop_input_file(void);
 			push_input_file(name);
 		}
 
-<*>^"#"(line)?{WS}+[0-9]+{WS}+{STRING}({WS}+[0-9]+)? {
+<*>^"#"(line)?{WS}+[0-9]+{WS}+{STRING}([ \t]+[0-9]+)? {
 			char *line, *tmp, *fn;
 			/* skip text before line # */
 			line = yytext;
diff --git a/tests/line_directives.dts b/tests/line_directives.dts
index e9d0800..046ef37 100644
--- a/tests/line_directives.dts
+++ b/tests/line_directives.dts
@@ -8,4 +8,14 @@ 
 # 6 "bar.dts"
 
 / {
+/*
+ * Make sure optional flags don't consume integer data on next line. The issue
+ * was that the {WS} in the trailing ({WS}+[0-9]+)? could cross the * line-
+ * break, and consume the leading "0" of the hex constant, leaving "x12345678"
+ * to be parsed as a number, which is invalid syntax.
+ */
+	prop1 = <
+# 10 "qux.dts"
+		0x12345678
+	>;
 };