From 07edff9265204e15c9fc8d07cc69e38c4c484e15 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Thu, 29 Oct 2020 12:32:16 +0100 Subject: [PATCH] vt: keyboard, reorder user buffer handling in vt_do_kdgkb_ioctl KDGKBSENT (the getter) needs only 'user_kdgkb->kb_func' from the userspace, i.e. the index. Then it needs a buffer for a local copy of 'kb_string'. KDSKBSENT (the setter) needs a copy up to the length of 'user_kdgkb->kb_string'. That means, we obtain the index before the switch-case and use it in both paths and: 1) allocate full space in the getter case, and 2) copy the string only in the setter case. We do it by strndup_user helper now which was not available when this function was written. Given we copy the two members of 'struct kbsentry' separately, we no longer need a local definition. Hence we need to change all the sizeofs here too. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20201029113222.32640-11-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/keyboard.c | 42 ++++++++++++++++++++---------------------- 1 file changed, 20 insertions(+), 22 deletions(-) diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c index 55014f5..81afe04 100644 --- a/drivers/tty/vt/keyboard.c +++ b/drivers/tty/vt/keyboard.c @@ -2021,7 +2021,7 @@ int vt_do_kdsk_ioctl(int cmd, struct kbentry __user *user_kbe, int perm, /* FIXME: This one needs untangling */ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) { - struct kbsentry *kbs; + char *kbs; u_char *q; int sz, fnw_sz; int delta; @@ -2034,39 +2034,37 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) if (!capable(CAP_SYS_TTY_CONFIG)) perm = 0; - kbs = kmalloc(sizeof(*kbs), GFP_KERNEL); - if (!kbs) { - ret = -ENOMEM; - goto reterr; - } + if (get_user(kb_func, &user_kdgkb->kb_func)) + return -EFAULT; - /* we mostly copy too much here (512bytes), but who cares ;) */ - if (copy_from_user(kbs, user_kdgkb, sizeof(struct kbsentry))) { - ret = -EFAULT; - goto reterr; - } - kbs->kb_string[sizeof(kbs->kb_string)-1] = '\0'; - kb_func = array_index_nospec(kbs->kb_func, MAX_NR_FUNC); + kb_func = array_index_nospec(kb_func, MAX_NR_FUNC); switch (cmd) { case KDGKBSENT: { /* size should have been a struct member */ ssize_t len = sizeof(user_kdgkb->kb_string); + kbs = kmalloc(len, GFP_KERNEL); + if (!kbs) + return -ENOMEM; + spin_lock_irqsave(&func_buf_lock, flags); - len = strlcpy(kbs->kb_string, func_table[kb_func] ? : "", len); + len = strlcpy(kbs, func_table[kb_func] ? : "", len); spin_unlock_irqrestore(&func_buf_lock, flags); - ret = copy_to_user(user_kdgkb->kb_string, kbs->kb_string, - len + 1) ? -EFAULT : 0; + ret = copy_to_user(user_kdgkb->kb_string, kbs, len + 1) ? + -EFAULT : 0; goto reterr; } case KDSKBSENT: - if (!perm) { - ret = -EPERM; - goto reterr; - } + if (!perm) + return -EPERM; + + kbs = strndup_user(user_kdgkb->kb_string, + sizeof(user_kdgkb->kb_string)); + if (IS_ERR(kbs)) + return PTR_ERR(kbs); fnw = NULL; fnw_sz = 0; @@ -2084,7 +2082,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) else fj = first_free; /* buffer usage increase by new entry */ - delta = (q ? -strlen(q) : 1) + strlen(kbs->kb_string); + delta = (q ? -strlen(q) : 1) + strlen(kbs); if (delta <= funcbufleft) { /* it fits in current buf */ if (j < MAX_NR_FUNC) { @@ -2136,7 +2134,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) funcbufsize = sz; } /* finally insert item itself */ - strcpy(func_table[kb_func], kbs->kb_string); + strcpy(func_table[kb_func], kbs); spin_unlock_irqrestore(&func_buf_lock, flags); break; } -- 2.7.4