DragonFly bugs List (threaded) for 2005-01
Re: Looks like split of execve(2) syscall created bugs
Another regression of execve() is that now it doesn't return error value
if NULL has been passed as its second argument.
Maxim Sobolev wrote:
I am working on eliminating stackgap in FreeBSD's linuxlator following
DF's footsteps and fond that there is potential bug has been introduced
into execve(). The problem is that DF now first checks if argv is
NULL, then replaces it with pathname and then proceeds with scanning
other arguments instead of stopping there. According to the comment in
the code, such behaviour has been introduced to make shell scripts
working. However there are two problems with this approach:
1. According to the POSIX, execve() should pass arguments list
unmodified to the newly created process. This means that if I invoke
execve with argv being NULL, the new image should see argc == 0 and
argv = NULL. DF in this case will copy the new image path as argv
and new image will see see it as argv/argc == 1.
2. In some cases, the new logic will result in bogus arguments passed to
the new image or EFAULT when first argument is NULL. This will happen
due to the bug in routine which copies arguments from the user space
into the kernel space. It assumes that both argv and argv are
NULL, while only former is required to be to stop processing.
The proper fix is to move special handling of argv == NULL case into
imgact_shell.c where it belongs.