[PATCH] kconfig: undefined symbols can crash dependency loop detection

[PATCH] kconfig: undefined symbols can crash dependency loop detection

[Ulf Magnusson]

The Kconfig

config FOO
	bool "FOO" if BAR
	select BAR

has a dependency loop involving an undefined symbol BAR. This causes a
segfault in sym_check_print_recursive() as it assumes all symbols have a
non-null 'prop', which is not the case for undefined symbols. This is a
proposed fix.

Signed-off-by: Ulf Magnusson <ulfalizer.lkml@gmail.com>
---
 scripts/kconfig/symbol.c |   32 ++++++++++++++++++++++++++++----
 1 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index a796c95..81a217f 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -5,6 +5,7 @@
 
 #include <ctype.h>
 #include <stdlib.h>
+#include <stdio.h>
 #include <string.h>
 #include <regex.h>
 #include <sys/utsname.h>
@@ -972,6 +973,10 @@ static void sym_check_print_recursive(struct symbol *last_sym)
 	struct menu *menu = NULL;
 	struct property *prop;
 	struct dep_stack cv_stack;
+	const char *filename;
+	int lineno;
+	char undef_msg_buf[100];
+	int snprintf_size;
 
 	if (sym_is_choice_value(last_sym)) {
 		dep_stack_insert(&cv_stack, last_sym);
@@ -1001,18 +1006,37 @@ static void sym_check_print_recursive(struct symbol *last_sym)
 					break;
 			}
 		}
+
+		if (prop) {
+			filename = prop->file->name;
+			lineno = prop->lineno;
+		} else {
+			/* The dependency loop involves an undefined symbol.
+			 * Checking sym->name is probably unnecessary here, but
+			 * just to be on the safe side. */
+			snprintf_size = snprintf(undef_msg_buf,
+						 sizeof(undef_msg_buf),
+						 "<no file, %s is undefined>",
+						 sym->name ? sym->name :
+							     "<choice>");
+			if (snprintf_size > sizeof(undef_msg_buf))
+				undef_msg_buf[sizeof(undef_msg_buf) - 1] = '\0';
+			filename = undef_msg_buf;
+			lineno = 0;
+		}
+
 		if (stack->sym == last_sym)
 			fprintf(stderr, "%s:%d:error: recursive dependency detected!\n",
-				prop->file->name, prop->lineno);
+				filename, lineno);
 		if (stack->expr) {
 			fprintf(stderr, "%s:%d:\tsymbol %s %s value contains %s\n",
-				prop->file->name, prop->lineno,
+				filename, lineno,
 				sym->name ? sym->name : "<choice>",
 				prop_get_type_name(prop->type),
 				next_sym->name ? next_sym->name : "<choice>");
 		} else if (stack->prop) {
 			fprintf(stderr, "%s:%d:\tsymbol %s depends on %s\n",
-				prop->file->name, prop->lineno,
+				filename, lineno,
 				sym->name ? sym->name : "<choice>",
 				next_sym->name ? next_sym->name : "<choice>");
 		} else if (sym_is_choice(sym)) {
@@ -1027,7 +1051,7 @@ static void sym_check_print_recursive(struct symbol *last_sym)
 				next_sym->name ? next_sym->name : "<choice>");
 		} else {
 			fprintf(stderr, "%s:%d:\tsymbol %s is selected by %s\n",
-				prop->file->name, prop->lineno,
+				filename, lineno,
 				sym->name ? sym->name : "<choice>",
 				next_sym->name ? next_sym->name : "<choice>");
 		}
-- 
1.7.0.4

Re: [PATCH] kconfig: undefined symbols can crash dependency loop detection

[Michal Marek]

On 5.2.2011 00:16, Ulf Magnusson wrote:
> The Kconfig
> 
> config FOO
> 	bool "FOO" if BAR
> 	select BAR
> 
> has a dependency loop involving an undefined symbol BAR. This causes a
> segfault in sym_check_print_recursive() as it assumes all symbols have a
> non-null 'prop', which is not the case for undefined symbols. This is a
> proposed fix.
> 
> Signed-off-by: Ulf Magnusson <ulfalizer.lkml@gmail.com>
> ---
>  scripts/kconfig/symbol.c |   32 ++++++++++++++++++++++++++++----
>  1 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
> index a796c95..81a217f 100644
> --- a/scripts/kconfig/symbol.c
> +++ b/scripts/kconfig/symbol.c
> @@ -5,6 +5,7 @@
>  
>  #include <ctype.h>
>  #include <stdlib.h>
> +#include <stdio.h>
>  #include <string.h>
>  #include <regex.h>
>  #include <sys/utsname.h>
> @@ -972,6 +973,10 @@ static void sym_check_print_recursive(struct symbol *last_sym)
>  	struct menu *menu = NULL;
>  	struct property *prop;
>  	struct dep_stack cv_stack;
> +	const char *filename;
> +	int lineno;
> +	char undef_msg_buf[100];
> +	int snprintf_size;
>  
>  	if (sym_is_choice_value(last_sym)) {
>  		dep_stack_insert(&cv_stack, last_sym);
> @@ -1001,18 +1006,37 @@ static void sym_check_print_recursive(struct symbol *last_sym)
>  					break;
>  			}
>  		}
> +
> +		if (prop) {
> +			filename = prop->file->name;
> +			lineno = prop->lineno;
> +		} else {
> +			/* The dependency loop involves an undefined symbol.
> +			 * Checking sym->name is probably unnecessary here, but
> +			 * just to be on the safe side. */
> +			snprintf_size = snprintf(undef_msg_buf,
> +						 sizeof(undef_msg_buf),
> +						 "<no file, %s is undefined>",
> +						 sym->name ? sym->name :
> +							     "<choice>");
> +			if (snprintf_size > sizeof(undef_msg_buf))
> +				undef_msg_buf[sizeof(undef_msg_buf) - 1] = '\0';
> +			filename = undef_msg_buf;
> +			lineno = 0;

Good catch. But as this handles a corner case involving a severely
borken Kconfig file, I would simply do
filename = "<unknown>";
lineno = 0;
and be done with it.

Michal

Re: [PATCH] kconfig: undefined symbols can crash dependency loop detection

[Ulf Magnusson]

On Thu, Feb 10, 2011 at 04:23:55PM +0100, Michal Marek wrote:
> On 5.2.2011 00:16, Ulf Magnusson wrote:
> > The Kconfig
> > 
> > config FOO
> > 	bool "FOO" if BAR
> > 	select BAR
> > 
> > has a dependency loop involving an undefined symbol BAR. This causes a
> > segfault in sym_check_print_recursive() as it assumes all symbols have a
> > non-null 'prop', which is not the case for undefined symbols. This is a
> > proposed fix.
> > 
> > Signed-off-by: Ulf Magnusson <ulfalizer.lkml@gmail.com>
> > ---
> >  scripts/kconfig/symbol.c |   32 ++++++++++++++++++++++++++++----
> >  1 files changed, 28 insertions(+), 4 deletions(-)
> > 
> > diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
> > index a796c95..81a217f 100644
> > --- a/scripts/kconfig/symbol.c
> > +++ b/scripts/kconfig/symbol.c
> > @@ -5,6 +5,7 @@
> >  
> >  #include <ctype.h>
> >  #include <stdlib.h>
> > +#include <stdio.h>
> >  #include <string.h>
> >  #include <regex.h>
> >  #include <sys/utsname.h>
> > @@ -972,6 +973,10 @@ static void sym_check_print_recursive(struct symbol *last_sym)
> >  	struct menu *menu = NULL;
> >  	struct property *prop;
> >  	struct dep_stack cv_stack;
> > +	const char *filename;
> > +	int lineno;
> > +	char undef_msg_buf[100];
> > +	int snprintf_size;
> >  
> >  	if (sym_is_choice_value(last_sym)) {
> >  		dep_stack_insert(&cv_stack, last_sym);
> > @@ -1001,18 +1006,37 @@ static void sym_check_print_recursive(struct symbol *last_sym)
> >  					break;
> >  			}
> >  		}
> > +
> > +		if (prop) {
> > +			filename = prop->file->name;
> > +			lineno = prop->lineno;
> > +		} else {
> > +			/* The dependency loop involves an undefined symbol.
> > +			 * Checking sym->name is probably unnecessary here, but
> > +			 * just to be on the safe side. */
> > +			snprintf_size = snprintf(undef_msg_buf,
> > +						 sizeof(undef_msg_buf),
> > +						 "<no file, %s is undefined>",
> > +						 sym->name ? sym->name :
> > +							     "<choice>");
> > +			if (snprintf_size > sizeof(undef_msg_buf))
> > +				undef_msg_buf[sizeof(undef_msg_buf) - 1] = '\0';
> > +			filename = undef_msg_buf;
> > +			lineno = 0;
> 
> Good catch. But as this handles a corner case involving a severely
> borken Kconfig file, I would simply do
> filename = "<unknown>";
> lineno = 0;
> and be done with it.
>
Yeah, it probably isn't very likely to occur in practise, though it
would also happen if a symbol selects an undefined symbol it depends on
via an enclosing menu or if.

Pick whatever version you prefer :)

/Ulf