Commit 9de1fec5 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Linus Torvalds
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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@linux.ibm.com:use strncpy_from_kernel_nofault() in fetch_store_string()]
  Link: http://lkml.kernel.org/r/20200606181903.49384-1-svens@linux.ibm.com



Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-15-hch@lst.de


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8d92db5c

kernel/trace/trace_kprobe.c

+43 −29
Original line number Diff line number Diff line
@@ -1200,6 +1200,15 @@ static const struct file_operations kprobe_profile_ops = { 


/* Kprobe specific fetch functions */



/* 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)
@@ -1207,30 +1216,27 @@ 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, void *dest, void *base) 


	__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);
@@ -1252,35 +1254,37 @@ fetch_store_string(unsigned long addr, void *dest, void *base) 
}



/*

 * 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);



	return ret;

}



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)

{
@@ -1289,6 +1293,16 @@ probe_mem_read_user(void *dest, void *src, size_t size) 
	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,

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