This is a note to let you know that I've just added the patch titled
x86/ibt,ftrace: Search for __fentry__ location
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-ibt-ftrace-search-for-__fentry__-location.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0fb3ba2981bdfeed49e23a1f6c7b020405952b3b
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Tue Mar 8 16:30:29 2022 +0100
x86/ibt,ftrace: Search for __fentry__ location
[ Upstream commit aebfd12521d9c7d0b502cf6d06314cfbcdccfe3b ]
Currently a lot of ftrace code assumes __fentry__ is at sym+0. However
with Intel IBT enabled the first instruction of a function will most
likely be ENDBR.
Change ftrace_location() to not only return the __fentry__ location
when called for the __fentry__ location, but also when called for the
sym+0 location.
Then audit/update all callsites of this function to consistently use
these new semantics.
Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220308154318.227581603@xxxxxxxxxxxxx
Stable-dep-of: e60b613df8b6 ("ftrace: Fix possible use-after-free issue in ftrace_location()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 893f040b97b7d..99dd504307fdc 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -194,17 +194,10 @@ static unsigned long
__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
{
struct kprobe *kp;
- unsigned long faddr;
+ bool faddr;
kp = get_kprobe((void *)addr);
- faddr = ftrace_location(addr);
- /*
- * Addresses inside the ftrace location are refused by
- * arch_check_ftrace_location(). Something went terribly wrong
- * if such an address is checked here.
- */
- if (WARN_ON(faddr && faddr != addr))
- return 0UL;
+ faddr = ftrace_location(addr) == addr;
/*
* Use the current code if it is not modified by Kprobe
* and it cannot be modified by ftrace.
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4fa75791b45e2..1bffee0458863 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -108,18 +108,6 @@ static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
tr->mod = NULL;
}
-static int is_ftrace_location(void *ip)
-{
- long addr;
-
- addr = ftrace_location((long)ip);
- if (!addr)
- return 0;
- if (WARN_ON_ONCE(addr != (long)ip))
- return -EFAULT;
- return 1;
-}
-
static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
{
void *ip = tr->func.addr;
@@ -151,12 +139,12 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
{
void *ip = tr->func.addr;
+ unsigned long faddr;
int ret;
- ret = is_ftrace_location(ip);
- if (ret < 0)
- return ret;
- tr->func.ftrace_managed = ret;
+ faddr = ftrace_location((unsigned long)ip);
+ if (faddr)
+ tr->func.ftrace_managed = true;
if (bpf_trampoline_module_get(tr))
return -ENOENT;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index af57705e1fef3..258d425b2c4a5 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1526,14 +1526,10 @@ static inline int warn_kprobe_rereg(struct kprobe *p)
int __weak arch_check_ftrace_location(struct kprobe *p)
{
- unsigned long ftrace_addr;
+ unsigned long addr = (unsigned long)p->addr;
- ftrace_addr = ftrace_location((unsigned long)p->addr);
- if (ftrace_addr) {
+ if (ftrace_location(addr) == addr) {
#ifdef CONFIG_KPROBES_ON_FTRACE
- /* Given address is not on the instruction boundary */
- if ((unsigned long)p->addr != ftrace_addr)
- return -EILSEQ;
p->flags |= KPROBE_FLAG_FTRACE;
#else /* !CONFIG_KPROBES_ON_FTRACE */
return -EINVAL;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 157a1d2d9802f..3dce1a107a7c7 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1575,17 +1575,34 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
}
/**
- * ftrace_location - return true if the ip giving is a traced location
+ * ftrace_location - return the ftrace location
* @ip: the instruction pointer to check
*
- * Returns rec->ip if @ip given is a pointer to a ftrace location.
- * That is, the instruction that is either a NOP or call to
- * the function tracer. It checks the ftrace internal tables to
- * determine if the address belongs or not.
+ * If @ip matches the ftrace location, return @ip.
+ * If @ip matches sym+0, return sym's ftrace location.
+ * Otherwise, return 0.
*/
unsigned long ftrace_location(unsigned long ip)
{
- return ftrace_location_range(ip, ip);
+ struct dyn_ftrace *rec;
+ unsigned long offset;
+ unsigned long size;
+
+ rec = lookup_rec(ip, ip);
+ if (!rec) {
+ if (!kallsyms_lookup_size_offset(ip, &size, &offset))
+ goto out;
+
+ /* map sym+0 to __fentry__ */
+ if (!offset)
+ rec = lookup_rec(ip, ip + size - 1);
+ }
+
+ if (rec)
+ return rec->ip;
+
+out:
+ return 0;
}
/**
@@ -4942,7 +4959,8 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
{
struct ftrace_func_entry *entry;
- if (!ftrace_location(ip))
+ ip = ftrace_location(ip);
+ if (!ip)
return -EINVAL;
if (remove) {
@@ -5090,11 +5108,16 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
struct ftrace_func_entry *entry;
struct ftrace_hash *free_hash = NULL;
struct dyn_ftrace *rec;
- int ret = -EBUSY;
+ int ret = -ENODEV;
mutex_lock(&direct_mutex);
+ ip = ftrace_location(ip);
+ if (!ip)
+ goto out_unlock;
+
/* See if there's a direct function at @ip already */
+ ret = -EBUSY;
if (ftrace_find_rec_direct(ip))
goto out_unlock;
@@ -5223,6 +5246,10 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
mutex_lock(&direct_mutex);
+ ip = ftrace_location(ip);
+ if (!ip)
+ goto out_unlock;
+
entry = find_direct_entry(&ip, NULL);
if (!entry)
goto out_unlock;
@@ -5354,6 +5381,11 @@ int modify_ftrace_direct(unsigned long ip,
mutex_lock(&direct_mutex);
mutex_lock(&ftrace_lock);
+
+ ip = ftrace_location(ip);
+ if (!ip)
+ goto out_unlock;
+
entry = find_direct_entry(&ip, &rec);
if (!entry)
goto out_unlock;
