Messages in this thread Patch in this message | | | From | Zheng Yejian <> | Subject | [PATCH v2] kprobes: Avoid possible warn in __arm_kprobe_ftrace() | Date | Mon, 8 Apr 2024 16:34:03 +0800 |
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There is once warn in __arm_kprobe_ftrace() on:
ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0); if (WARN_ONCE(..., "Failed to arm kprobe-ftrace at %pS (error %d)\n", ...) return ret;
This warning is generated because 'p->addr' is detected to be not a valid ftrace location in ftrace_set_filter_ip(). The ftrace address check is done by check_ftrace_location() at the beginning of check_kprobe_address_safe(). At that point, ftrace_location(addr) == addr should return true if the module is loaded. Then the module is searched twice: 1. in is_module_text_address(), we find that 'p->addr' is in a module; 2. in __module_text_address(), we find the module;
If the module has just been unloaded before the second search, then '*probed_mod' is NULL and we would not go to get the module refcount, then the return value of check_kprobe_address_safe() would be 0, but actually we need to return -EINVAL.
To fix it, originally we can simply check 'p->addr' is out of text again, like below. But that would check twice respectively in kernel text and module text, so finally I reduce them to be once.
if (!(core_kernel_text((unsigned long) p->addr) || is_module_text_address((unsigned long) p->addr)) || ...) { ret = -EINVAL; goto out; } ... *probed_mod = __module_text_address((unsigned long) p->addr); if (*probed_mod) { ... } else if (!core_kernel_text((unsigned long) p->addr)) { // check again! ret = -EINVAL; goto out; }
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> --- kernel/kprobes.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
v2: - Update commit messages and comments as suggested by Masami. Link: https://lore.kernel.org/all/20240408115038.b0c85767bf1f249eccc32fff@kernel.org/
v1: - Link: https://lore.kernel.org/all/20240407035904.2556645-1-zhengyejian1@huawei.com/
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 9d9095e81792..65adc815fc6e 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1567,10 +1567,17 @@ static int check_kprobe_address_safe(struct kprobe *p, jump_label_lock(); preempt_disable(); - /* Ensure it is not in reserved area nor out of text */ - if (!(core_kernel_text((unsigned long) p->addr) || - is_module_text_address((unsigned long) p->addr)) || - in_gate_area_no_mm((unsigned long) p->addr) || + /* Ensure the address is in a text area, and find a module if exists. */ + *probed_mod = NULL; + if (!core_kernel_text((unsigned long) p->addr)) { + *probed_mod = __module_text_address((unsigned long) p->addr); + if (!(*probed_mod)) { + ret = -EINVAL; + goto out; + } + } + /* Ensure it is not in reserved area. */ + if (in_gate_area_no_mm((unsigned long) p->addr) || within_kprobe_blacklist((unsigned long) p->addr) || jump_label_text_reserved(p->addr, p->addr) || static_call_text_reserved(p->addr, p->addr) || @@ -1580,8 +1587,7 @@ static int check_kprobe_address_safe(struct kprobe *p, goto out; } - /* Check if 'p' is probing a module. */ - *probed_mod = __module_text_address((unsigned long) p->addr); + /* Get module refcount and reject __init functions for loaded modules. */ if (*probed_mod) { /* * We must hold a refcount of the probed module while updating -- 2.25.1
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