Hi Hangyu,
On 13/1/22 11:58 am, Hangyu Hua wrote:
When the size of commandp >= size, array out of bound write occurs because
len == 0.
Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
---
arch/m68k/kernel/uboot.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/m68k/kernel/uboot.c b/arch/m68k/kernel/uboot.c
index 928dbd33fc4a..63eaf3c3ddcd 100644
--- a/arch/m68k/kernel/uboot.c
+++ b/arch/m68k/kernel/uboot.c
@@ -101,5 +101,6 @@ __init void process_uboot_commandline(char *commandp, int size)
}
parse_uboot_commandline(commandp, len);
- commandp[len - 1] = 0;
+ if (len > 0)
+ commandp[len - 1] = 0;
}
I am not convinced this is wrong for the reason you think it is.
Looking at the code in its entirety:
__init void process_uboot_commandline(char *commandp, int size)
{
int len, n;
n = strnlen(commandp, size);
commandp += n;
len = size - n;
if (len) {
/* Add the whitespace separator */
*commandp++ = ' ';
len--;
}
parse_uboot_commandline(commandp, len);
commandp[len - 1] = 0;
}
"commandp" is moved based on the return of the strnlen(). So in the
case of commandp actually being full of valid characters (so n == size,
and thus len == 0) the commandp technically points outside of its
real size at that point. But "command[[len - 1]" would actually be
pointing to the last char in the original commandp array (so the original
commandp[size - 1]). Well at least if you are happy with the use of
negative array indexes.
Clearly this could be structured better. There is no point in calling
parse_uboot_commandline() if len == 0, or even if len == 1, since you
cannot add anymore to the command line, it is full.
Regards
Greg
