Re: [PATCH] arm64: ftrace: don't dereference a probably invalid address
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2021-06-07 13:55:23
Also in:
linux-arm-kernel, lkml
On Mon, 7 Jun 2021 11:23:30 +0800 Mark-PK Tsai [off-list ref] wrote:
Address in __mcount_loc may be invalid if somthing goes wrong. On our arm64 platform, the bug in recordmcount make kernel crash in ftrace_init().
How did it crash? The link below doesn't show any crash.
https://lore.kernel.org/lkml/20210607023839.26387-1-mark-pk.tsai@mediatek.com/ (local) Return -EFAULT if we are dealing with out-of-range condition to prevent dereference the invalid address in ftrace_bug(), then the kernel can disable ftrace safely for problematic __mcount_loc.
!mod is not an out-of-range condition. It just happened that the other bug caused this strange side-effect. A !mod does not mean a fault happened. Just because it may have been caused by a fault in your use case does not mean that it's a fault in all use cases. That's like saying that your dog is a poodle, so all dogs are poodles. A return of -EINVAL should not cause a crash. If it does, then that needs to be fixed. -- Steve
quoted hunk ↗ jump to hunk
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> --- arch/arm64/kernel/ftrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index b5d3ddaf69d9..98bec8445a58 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c@@ -201,7 +201,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, preempt_enable(); if (WARN_ON(!mod)) - return -EINVAL; + return -EFAULT; } /*
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