The patch titled
modules: make module_address_lookup safe
has been added to the -mm tree. Its filename is
modules-make-module_address_lookup-safe.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: modules: make module_address_lookup safe
From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
module_address_lookup releases preemption then returns a pointer into the
module space. The only user (kallsyms) copies the result, so just do that
under the preempt disable.
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Kyle McMartin <kyle@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/module.h | 22 +++++++++++++---------
kernel/kallsyms.c | 11 ++++-------
kernel/module.c | 20 ++++++++++++--------
3 files changed, 29 insertions(+), 24 deletions(-)
diff -puN include/linux/module.h~modules-make-module_address_lookup-safe include/linux/module.h
--- a/include/linux/module.h~modules-make-module_address_lookup-safe
+++ a/include/linux/module.h
@@ -446,11 +446,14 @@ static inline void __module_get(struct m
__mod ? __mod->name : "kernel"; \
})
-/* For kallsyms to ask for address resolution. NULL means not found. */
-const char *module_address_lookup(unsigned long addr,
- unsigned long *symbolsize,
- unsigned long *offset,
- char **modname);
+/* For kallsyms to ask for address resolution. namebuf should be at
+ * least KSYM_NAME_LEN long: a pointer to namebuf is returned if
+ * found, otherwise NULL. */
+char *module_address_lookup(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf);
int lookup_module_symbol_name(unsigned long addr, char *symname);
int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
@@ -516,10 +519,11 @@ static inline void module_put(struct mod
#define module_name(mod) "kernel"
/* For kallsyms to ask for address resolution. NULL means not found. */
-static inline const char *module_address_lookup(unsigned long addr,
- unsigned long *symbolsize,
- unsigned long *offset,
- char **modname)
+static inline char *module_address_lookup(unsigned long addr,
+ unsigned long *symbolsize,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf)
{
return NULL;
}
diff -puN kernel/kallsyms.c~modules-make-module_address_lookup-safe kernel/kallsyms.c
--- a/kernel/kallsyms.c~modules-make-module_address_lookup-safe
+++ a/kernel/kallsyms.c
@@ -224,10 +224,11 @@ static unsigned long get_symbol_pos(unsi
int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
unsigned long *offset)
{
+ char namebuf[KSYM_NAME_LEN];
if (is_ksym_addr(addr))
return !!get_symbol_pos(addr, symbolsize, offset);
- return !!module_address_lookup(addr, symbolsize, offset, NULL);
+ return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
}
/*
@@ -242,8 +243,6 @@ const char *kallsyms_lookup(unsigned lon
unsigned long *offset,
char **modname, char *namebuf)
{
- const char *msym;
-
namebuf[KSYM_NAME_LEN - 1] = 0;
namebuf[0] = 0;
@@ -259,10 +258,8 @@ const char *kallsyms_lookup(unsigned lon
}
/* see if it's in a module */
- msym = module_address_lookup(addr, symbolsize, offset, modname);
- if (msym)
- return strncpy(namebuf, msym, KSYM_NAME_LEN - 1);
-
+ return module_address_lookup(addr, symbolsize, offset, modname,
+ namebuf);
return NULL;
}
diff -puN kernel/module.c~modules-make-module_address_lookup-safe kernel/module.c
--- a/kernel/module.c~modules-make-module_address_lookup-safe
+++ a/kernel/module.c
@@ -2215,14 +2215,13 @@ static const char *get_ksymbol(struct mo
return mod->strtab + mod->symtab[best].st_name;
}
-/* For kallsyms to ask for address resolution. NULL means not found.
- We don't lock, as this is used for oops resolution and races are a
- lesser concern. */
-/* FIXME: Risky: returns a pointer into a module w/o lock */
-const char *module_address_lookup(unsigned long addr,
- unsigned long *size,
- unsigned long *offset,
- char **modname)
+/* For kallsyms to ask for address resolution. NULL means not found. Careful
+ * not to lock to avoid deadlock on oopses, simply disable preemption. */
+char *module_address_lookup(unsigned long addr,
+ unsigned long *size,
+ unsigned long *offset,
+ char **modname,
+ char *namebuf)
{
struct module *mod;
const char *ret = NULL;
@@ -2237,6 +2236,11 @@ const char *module_address_lookup(unsign
break;
}
}
+ /* Make a copy in here where it's safe */
+ if (ret) {
+ strncpy(namebuf, ret, KSYM_NAME_LEN - 1);
+ ret = namebuf;
+ }
preempt_enable();
return ret;
}
_
Patches currently in -mm which might be from rusty@xxxxxxxxxxxxxxx are
git-kbuild.patch
git-kvm.patch
git-libata-all.patch
git-scsi-misc.patch
kallsyms-should-prefer-non-weak-symbols.patch
virtio_net-remove-double-ether_setup.patch
modules-handle-symbols-that-have-a-zero-value.patch
modules-include-sectionsh-to-avoid-defining-linker-variables.patch
modules-fold-percpu_modcopy-into-modulec-and-get-rid-of-the-macro-from-hell.patch
modules-de-mutex-more-symbol-lookup-paths-in-the-module-code.patch
modules-make-module_address_lookup-safe.patch
reiser4.patch
-
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