From: Christoph Hellwig <hch@xxxxxx> Subject: tracing/kprobes: handle mixed kernel/userspace probes better Instead of using the dangerous probe_kernel_read and strncpy_from_unsafe helpers, rework probes to try a user probe based on the address if the architecture has a common address space for kernel and userspace. [svens@xxxxxxxxxxxxx:use strncpy_from_kernel_nofault() in fetch_store_string()] Link: http://lkml.kernel.org/r/20200606181903.49384-1-svens@xxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200521152301.2587579-15-hch@xxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/trace/trace_kprobe.c | 72 ++++++++++++++++++++-------------- 1 file changed, 43 insertions(+), 29 deletions(-) --- a/kernel/trace/trace_kprobe.c~tracing-kprobes-handle-mixed-kernel-userspace-probes-better +++ a/kernel/trace/trace_kprobe.c @@ -1202,35 +1202,41 @@ static const struct file_operations kpro /* Return the length of string -- including null terminal byte */ static nokprobe_inline int +fetch_store_strlen_user(unsigned long addr) +{ + const void __user *uaddr = (__force const void __user *)addr; + + return strnlen_user_nofault(uaddr, MAX_STRING_SIZE); +} + +/* Return the length of string -- including null terminal byte */ +static nokprobe_inline int fetch_store_strlen(unsigned long addr) { int ret, len = 0; u8 c; +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE + if (addr < TASK_SIZE) + return fetch_store_strlen_user(addr); +#endif + do { - ret = probe_kernel_read(&c, (u8 *)addr + len, 1); + ret = probe_kernel_read_strict(&c, (u8 *)addr + len, 1); len++; } while (c && ret == 0 && len < MAX_STRING_SIZE); return (ret < 0) ? ret : len; } -/* Return the length of string -- including null terminal byte */ -static nokprobe_inline int -fetch_store_strlen_user(unsigned long addr) -{ - const void __user *uaddr = (__force const void __user *)addr; - - return strnlen_user_nofault(uaddr, MAX_STRING_SIZE); -} - /* - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max - * length and relative data location. + * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf + * with max length and relative data location. */ static nokprobe_inline int -fetch_store_string(unsigned long addr, void *dest, void *base) +fetch_store_string_user(unsigned long addr, void *dest, void *base) { + const void __user *uaddr = (__force const void __user *)addr; int maxlen = get_loc_len(*(u32 *)dest); void *__dest; long ret; @@ -1240,11 +1246,7 @@ fetch_store_string(unsigned long addr, v __dest = get_loc_data(dest, base); - /* - * Try to get string again, since the string can be changed while - * probing. - */ - ret = strncpy_from_unsafe(__dest, (void *)addr, maxlen); + ret = strncpy_from_user_nofault(__dest, uaddr, maxlen); if (ret >= 0) *(u32 *)dest = make_data_loc(ret, __dest - base); @@ -1252,23 +1254,31 @@ fetch_store_string(unsigned long addr, v } /* - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf - * with max length and relative data location. + * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max + * length and relative data location. */ static nokprobe_inline int -fetch_store_string_user(unsigned long addr, void *dest, void *base) +fetch_store_string(unsigned long addr, void *dest, void *base) { - const void __user *uaddr = (__force const void __user *)addr; int maxlen = get_loc_len(*(u32 *)dest); void *__dest; long ret; +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE + if ((unsigned long)addr < TASK_SIZE) + return fetch_store_string_user(addr, dest, base); +#endif + if (unlikely(!maxlen)) return -ENOMEM; __dest = get_loc_data(dest, base); - ret = strncpy_from_user_nofault(__dest, uaddr, maxlen); + /* + * Try to get string again, since the string can be changed while + * probing. + */ + ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen); if (ret >= 0) *(u32 *)dest = make_data_loc(ret, __dest - base); @@ -1276,12 +1286,6 @@ fetch_store_string_user(unsigned long ad } static nokprobe_inline int -probe_mem_read(void *dest, void *src, size_t size) -{ - return probe_kernel_read(dest, src, size); -} - -static nokprobe_inline int probe_mem_read_user(void *dest, void *src, size_t size) { const void __user *uaddr = (__force const void __user *)src; @@ -1289,6 +1293,16 @@ probe_mem_read_user(void *dest, void *sr return probe_user_read(dest, uaddr, size); } +static nokprobe_inline int +probe_mem_read(void *dest, void *src, size_t size) +{ +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE + if ((unsigned long)src < TASK_SIZE) + return probe_mem_read_user(dest, src, size); +#endif + return probe_kernel_read_strict(dest, src, size); +} + /* Note that we don't verify it, since the code does not come from user space */ static int process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest, _
