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vt: Replace strlcpy with strscpy
strlcpy() reads the entire source buffer first and returns the size of the source string, not the destination string, which can be accidentally misused [1]. The copy_to_user() call uses @len returned from strlcpy() directly without checking its value. This could potentially lead to read overflow. There is no existing bug since @len is always guaranteed to be greater than hardcoded strings in @func_table[kb_func]. But as written it is very fragile and specifically uses a strlcpy() result without sanity checking and using it to copy to userspace. In an effort to remove strlcpy() completely [2], replace strlcpy() here with strscpy(). [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [2] https://github.com/KSPP/linux/issues/89 Signed-off-by: Azeem Shaikh <azeems@google.com> Reviewed-by: Justin Stitt <justinstitt@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20230919192156.121503-1-azeems@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 5 additions and 2 deletions
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@ -2079,12 +2079,15 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
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return -ENOMEM;
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spin_lock_irqsave(&func_buf_lock, flags);
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len = strlcpy(kbs, func_table[kb_func] ? : "", len);
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len = strscpy(kbs, func_table[kb_func] ? : "", len);
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spin_unlock_irqrestore(&func_buf_lock, flags);
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if (len < 0) {
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ret = -ENOSPC;
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break;
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}
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ret = copy_to_user(user_kdgkb->kb_string, kbs, len + 1) ?
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-EFAULT : 0;
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break;
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}
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case KDSKBSENT:
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