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authorSrinivasa Ds2008-04-28 11:14:26 +0200
committerLinus Torvalds2008-04-28 17:58:32 +0200
commit3d8d996e0ca5b4093203d3f050b0f70b5c949ae8 (patch)
tree2b19d3a47bf723c3bf6ff7c8a0d90078feaee08c /kernel/kprobes.c
parentVT notifier extension for accessibility (diff)
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kprobes: prevent probing of preempt_schedule()
Prohibit users from probing preempt_schedule(). One way of prohibiting the user from probing functions is by marking such functions with __kprobes. But this method doesn't work for those functions, which are already marked to different section like preempt_schedule() (belongs to __sched section). So we use blacklist approach to refuse user from probing these functions. In blacklist approach we populate the blacklisted function's starting address and its size in kprobe_blacklist structure. Then we verify the user specified address against start and end of the blacklisted function. So any attempt to register probe on blacklisted functions will be rejected. [akpm@linux-foundation.org: build fix] [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Jim Keniston <jkenisto@us.ibm.com> Cc: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/kprobes.c')
-rw-r--r--kernel/kprobes.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index fcfb580c3afc..f02a4311768b 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -72,6 +72,18 @@ DEFINE_MUTEX(kprobe_mutex); /* Protects kprobe_table */
DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */
static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
+/*
+ * Normally, functions that we'd want to prohibit kprobes in, are marked
+ * __kprobes. But, there are cases where such functions already belong to
+ * a different section (__sched for preempt_schedule)
+ *
+ * For such cases, we now have a blacklist
+ */
+struct kprobe_blackpoint kprobe_blacklist[] = {
+ {"preempt_schedule",},
+ {NULL} /* Terminator */
+};
+
#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
/*
* kprobe->ainsn.insn points to the copy of the instruction to be
@@ -492,9 +504,22 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
static int __kprobes in_kprobes_functions(unsigned long addr)
{
+ struct kprobe_blackpoint *kb;
+
if (addr >= (unsigned long)__kprobes_text_start &&
addr < (unsigned long)__kprobes_text_end)
return -EINVAL;
+ /*
+ * If there exists a kprobe_blacklist, verify and
+ * fail any probe registration in the prohibited area
+ */
+ for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
+ if (kb->start_addr) {
+ if (addr >= kb->start_addr &&
+ addr < (kb->start_addr + kb->range))
+ return -EINVAL;
+ }
+ }
return 0;
}
@@ -811,6 +836,11 @@ void __kprobes unregister_kretprobe(struct kretprobe *rp)
static int __init init_kprobes(void)
{
int i, err = 0;
+ unsigned long offset = 0, size = 0;
+ char *modname, namebuf[128];
+ const char *symbol_name;
+ void *addr;
+ struct kprobe_blackpoint *kb;
/* FIXME allocate the probe table, currently defined statically */
/* initialize all list heads */
@@ -819,6 +849,28 @@ static int __init init_kprobes(void)
INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
}
+ /*
+ * Lookup and populate the kprobe_blacklist.
+ *
+ * Unlike the kretprobe blacklist, we'll need to determine
+ * the range of addresses that belong to the said functions,
+ * since a kprobe need not necessarily be at the beginning
+ * of a function.
+ */
+ for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
+ kprobe_lookup_name(kb->name, addr);
+ if (!addr)
+ continue;
+
+ kb->start_addr = (unsigned long)addr;
+ symbol_name = kallsyms_lookup(kb->start_addr,
+ &size, &offset, &modname, namebuf);
+ if (!symbol_name)
+ kb->range = 0;
+ else
+ kb->range = size;
+ }
+
if (kretprobe_blacklist_size) {
/* lookup the function address from its name */
for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {