From: Christoph Hellwig <hch@xxxxxx> Subject: maccess: return -ERANGE when probe_kernel_read() fails Allow the callers to distinguish a real unmapped address vs a range that can't be probed. Link: http://lkml.kernel.org/r/20200521152301.2587579-24-hch@xxxxxx Signed-off-by: Christoph Hellwig <hch@xxxxxx> Suggested-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/maccess.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) --- a/mm/maccess.c~maccess-return-erange-when-copy_from_kernel_nofault_allowed-fails +++ a/mm/maccess.c @@ -24,7 +24,7 @@ bool __weak probe_kernel_read_allowed(co long probe_kernel_read(void *dst, const void *src, size_t size) { if (!probe_kernel_read_allowed(src, size)) - return -EFAULT; + return -ERANGE; pagefault_disable(); probe_kernel_read_loop(dst, src, size, u64, Efault); @@ -68,7 +68,7 @@ long strncpy_from_kernel_nofault(char *d if (unlikely(count <= 0)) return 0; if (!probe_kernel_read_allowed(unsafe_addr, count)) - return -EFAULT; + return -ERANGE; pagefault_disable(); do { @@ -93,7 +93,8 @@ Efault: * @size: size of the data chunk * * Safely read from kernel address @src to the buffer at @dst. If a kernel - * fault happens, handle that and return -EFAULT. + * fault happens, handle that and return -EFAULT. If @src is not a valid kernel + * address, return -ERANGE. * * We ensure that the copy_from_user is executed in atomic context so that * do_page_fault() doesn't attempt to take mmap_lock. This makes @@ -106,7 +107,7 @@ long probe_kernel_read(void *dst, const mm_segment_t old_fs = get_fs(); if (!probe_kernel_read_allowed(src, size)) - return -EFAULT; + return -ERANGE; set_fs(KERNEL_DS); pagefault_disable(); @@ -158,8 +159,9 @@ long probe_kernel_write(void *dst, const * * On success, returns the length of the string INCLUDING the trailing NUL. * - * If access fails, returns -EFAULT (some data may have been copied - * and the trailing NUL added). + * If access fails, returns -EFAULT (some data may have been copied and the + * trailing NUL added). If @unsafe_addr is not a valid kernel address, return + * -ERANGE. * * If @count is smaller than the length of the string, copies @count-1 bytes, * sets the last byte of @dst buffer to NUL and returns @count. @@ -173,7 +175,7 @@ long strncpy_from_kernel_nofault(char *d if (unlikely(count <= 0)) return 0; if (!probe_kernel_read_allowed(unsafe_addr, count)) - return -EFAULT; + return -ERANGE; set_fs(KERNEL_DS); pagefault_disable(); _
