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


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