Messages in this thread Patch in this message | | | From | Arvind Sankar <> | Subject | [RFC PATCH 2/2] x86/cmdline: Use strscpy to initialize boot_command_line | Date | Sat, 5 Sep 2020 18:23:23 -0400 |
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The x86 boot protocol requires the kernel command line to be a NUL-terminated string of length at most COMMAND_LINE_SIZE (including the terminating NUL). In case the bootloader messed up and the command line is too long (hence not NUL-terminated), use strscpy to copy the command line into boot_command_line. This ensures that boot_command_line is NUL-terminated, and it also avoids accessing beyond the actual end of the command line if it was properly NUL-terminated.
Note that setup_arch() will already force command_line to be NUL-terminated by using strlcpy(), as well as boot_command_line if a builtin command line is configured. If boot_command_line was not initially NUL-terminated, the strlen() inside of strlcpy()/strlcat() will run beyond boot_command_line, but this is almost certainly harmless in practice.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> --- arch/x86/kernel/head64.c | 2 +- arch/x86/kernel/head_32.S | 11 +++++------ 2 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index cbb71c1b574f..740dd05b9462 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -410,7 +410,7 @@ static void __init copy_bootdata(char *real_mode_data) cmd_line_ptr = get_cmd_line_ptr(); if (cmd_line_ptr) { command_line = __va(cmd_line_ptr); - memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE); + strscpy(boot_command_line, command_line, COMMAND_LINE_SIZE); } /* diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 7ed84c282233..2a7ced159d6b 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -102,13 +102,12 @@ SYM_CODE_START(startup_32) cld rep movsl - movl pa(boot_params) + NEW_CL_POINTER,%esi - andl %esi,%esi + movl pa(boot_params) + NEW_CL_POINTER,%edx + testl %edx,%edx jz 1f # No command line - movl $pa(boot_command_line),%edi - movl $(COMMAND_LINE_SIZE/4),%ecx - rep - movsl + movl $pa(boot_command_line),%eax + movl $COMMAND_LINE_SIZE,%ecx + call strscpy 1: #ifdef CONFIG_OLPC -- 2.26.2
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