| Message ID | 20200521165641.15940-9-kristen@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Function Granular KASLR | expand |
On Thu, May 21, 2020 at 09:56:39AM -0700, Kristen Carlson Accardi wrote: > This patch makes /proc/kallsyms display alphabetically by symbol > name rather than sorted by address in order to hide the newly > randomized address layout. > > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > Tested-by: Tony Luck <tony.luck@intel.com> > --- > kernel/kallsyms.c | 138 +++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 137 insertions(+), 1 deletion(-) > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index 16c8c605f4b0..558963b275ec 100644 > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -25,6 +25,7 @@ > #include <linux/filter.h> > #include <linux/ftrace.h> > #include <linux/compiler.h> > +#include <linux/list_sort.h> > > /* > * These will be re-linked against their real values > @@ -446,6 +447,11 @@ struct kallsym_iter { > int show_value; > }; > > +struct kallsyms_iter_list { > + struct kallsym_iter iter; > + struct list_head next; > +}; > + > int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, > char *type, char *name) > { > @@ -660,6 +666,121 @@ int kallsyms_show_value(void) > } > } > > +static int sorted_show(struct seq_file *m, void *p) > +{ > + struct list_head *list = m->private; > + struct kallsyms_iter_list *iter; > + int rc; > + > + if (list_empty(list)) > + return 0; > + > + iter = list_first_entry(list, struct kallsyms_iter_list, next); > + > + m->private = iter; > + rc = s_show(m, p); > + m->private = list; > + > + list_del(&iter->next); > + kfree(iter); > + > + return rc; > +} > + > +static void *sorted_start(struct seq_file *m, loff_t *pos) > +{ > + return m->private; > +} > + > +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos) > +{ > + struct list_head *list = m->private; > + > + (*pos)++; > + > + if (list_empty(list)) > + return NULL; > + > + return p; > +} > + > +static const struct seq_operations kallsyms_sorted_op = { > + .start = sorted_start, > + .next = sorted_next, > + .stop = s_stop, > + .show = sorted_show > +}; > + > +static int kallsyms_list_cmp(void *priv, struct list_head *a, > + struct list_head *b) > +{ > + struct kallsyms_iter_list *iter_a, *iter_b; > + > + iter_a = list_entry(a, struct kallsyms_iter_list, next); > + iter_b = list_entry(b, struct kallsyms_iter_list, next); > + > + return strcmp(iter_a->iter.name, iter_b->iter.name); > +} > + > +int get_all_symbol_name(void *data, const char *name, struct module *mod, > + unsigned long addr) > +{ > + unsigned long sym_pos; > + struct kallsyms_iter_list *node, *last; > + struct list_head *head = (struct list_head *)data; > + > + node = kmalloc(sizeof(*node), GFP_KERNEL); > + if (!node) > + return -ENOMEM; > + > + if (list_empty(head)) { > + sym_pos = 0; > + memset(node, 0, sizeof(*node)); > + reset_iter(&node->iter, 0); > + node->iter.show_value = kallsyms_show_value(); > + } else { > + last = list_first_entry(head, struct kallsyms_iter_list, next); > + memcpy(node, last, sizeof(*node)); > + sym_pos = last->iter.pos; > + } > + > + INIT_LIST_HEAD(&node->next); > + list_add(&node->next, head); > + > + /* > + * update_iter returns false when at end of file > + * which in this case we don't care about and can > + * safely ignore. update_iter() will increment > + * the value of iter->pos, for ksymbol_core. > + */ > + if (sym_pos >= kallsyms_num_syms) > + sym_pos++; > + > + (void)update_iter(&node->iter, sym_pos); > + > + return 0; > +} > + > +static int kallsyms_sorted_open(struct inode *inode, struct file *file) > +{ > + int ret; > + struct list_head *list; > + > + list = __seq_open_private(file, &kallsyms_sorted_op, sizeof(*list)); > + if (!list) > + return -ENOMEM; > + > + INIT_LIST_HEAD(list); > + > + ret = kallsyms_on_each_symbol(get_all_symbol_name, list); > + if (ret != 0) > + return ret; > + > + list_sort(NULL, list, kallsyms_list_cmp); > + > + return 0; > +} > + > static int kallsyms_open(struct inode *inode, struct file *file) > { > /* > @@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops = { > .proc_release = seq_release_private, > }; > > +static const struct proc_ops kallsyms_sorted_proc_ops = { > + .proc_open = kallsyms_sorted_open, > + .proc_read = seq_read, > + .proc_lseek = seq_lseek, > + .proc_release = seq_release_private, > +}; > + > static int __init kallsyms_init(void) > { > - proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); > + /* > + * When fine grained kaslr is enabled, we need to > + * print out the symbols sorted by name rather than by > + * by address, because this reveals the randomization order. > + */ > + if (!IS_ENABLED(CONFIG_FG_KASLR)) > + proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); > + else > + proc_create("kallsyms", 0444, NULL, &kallsyms_sorted_proc_ops); > return 0; Since this is compile-time selected, instead of the separate name and test here, how about just redefine kallsyms_open initializer instead? #ifdef CONFIG_FG_KASLR ...sorting routines... static int kallsyms_open(struct inode *inode, struct file *file) { ... sorted version ... } #else static int kallsyms_open(struct inode *inode, struct file *file) { ... normal version ... } #endif (And then just move the comment to the sorted open version.)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 16c8c605f4b0..558963b275ec 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -25,6 +25,7 @@ #include <linux/filter.h> #include <linux/ftrace.h> #include <linux/compiler.h> +#include <linux/list_sort.h> /* * These will be re-linked against their real values @@ -446,6 +447,11 @@ struct kallsym_iter { int show_value; }; +struct kallsyms_iter_list { + struct kallsym_iter iter; + struct list_head next; +}; + int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, char *type, char *name) { @@ -660,6 +666,121 @@ int kallsyms_show_value(void) } } +static int sorted_show(struct seq_file *m, void *p) +{ + struct list_head *list = m->private; + struct kallsyms_iter_list *iter; + int rc; + + if (list_empty(list)) + return 0; + + iter = list_first_entry(list, struct kallsyms_iter_list, next); + + m->private = iter; + rc = s_show(m, p); + m->private = list; + + list_del(&iter->next); + kfree(iter); + + return rc; +} + +static void *sorted_start(struct seq_file *m, loff_t *pos) +{ + return m->private; +} + +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos) +{ + struct list_head *list = m->private; + + (*pos)++; + + if (list_empty(list)) + return NULL; + + return p; +} + +static const struct seq_operations kallsyms_sorted_op = { + .start = sorted_start, + .next = sorted_next, + .stop = s_stop, + .show = sorted_show +}; + +static int kallsyms_list_cmp(void *priv, struct list_head *a, + struct list_head *b) +{ + struct kallsyms_iter_list *iter_a, *iter_b; + + iter_a = list_entry(a, struct kallsyms_iter_list, next); + iter_b = list_entry(b, struct kallsyms_iter_list, next); + + return strcmp(iter_a->iter.name, iter_b->iter.name); +} + +int get_all_symbol_name(void *data, const char *name, struct module *mod, + unsigned long addr) +{ + unsigned long sym_pos; + struct kallsyms_iter_list *node, *last; + struct list_head *head = (struct list_head *)data; + + node = kmalloc(sizeof(*node), GFP_KERNEL); + if (!node) + return -ENOMEM; + + if (list_empty(head)) { + sym_pos = 0; + memset(node, 0, sizeof(*node)); + reset_iter(&node->iter, 0); + node->iter.show_value = kallsyms_show_value(); + } else { + last = list_first_entry(head, struct kallsyms_iter_list, next); + memcpy(node, last, sizeof(*node)); + sym_pos = last->iter.pos; + } + + INIT_LIST_HEAD(&node->next); + list_add(&node->next, head); + + /* + * update_iter returns false when at end of file + * which in this case we don't care about and can + * safely ignore. update_iter() will increment + * the value of iter->pos, for ksymbol_core. + */ + if (sym_pos >= kallsyms_num_syms) + sym_pos++; + + (void)update_iter(&node->iter, sym_pos); + + return 0; +} + +static int kallsyms_sorted_open(struct inode *inode, struct file *file) +{ + int ret; + struct list_head *list; + + list = __seq_open_private(file, &kallsyms_sorted_op, sizeof(*list)); + if (!list) + return -ENOMEM; + + INIT_LIST_HEAD(list); + + ret = kallsyms_on_each_symbol(get_all_symbol_name, list); + if (ret != 0) + return ret; + + list_sort(NULL, list, kallsyms_list_cmp); + + return 0; +} + static int kallsyms_open(struct inode *inode, struct file *file) { /* @@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops = { .proc_release = seq_release_private, }; +static const struct proc_ops kallsyms_sorted_proc_ops = { + .proc_open = kallsyms_sorted_open, + .proc_read = seq_read, + .proc_lseek = seq_lseek, + .proc_release = seq_release_private, +}; + static int __init kallsyms_init(void) { - proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); + /* + * When fine grained kaslr is enabled, we need to + * print out the symbols sorted by name rather than by + * by address, because this reveals the randomization order. + */ + if (!IS_ENABLED(CONFIG_FG_KASLR)) + proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); + else + proc_create("kallsyms", 0444, NULL, &kallsyms_sorted_proc_ops); return 0; } device_initcall(kallsyms_init);