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tty: wipe buffer if not echoing data 

If we are not echoing the data to userspace or the console is in icanon
mode, then perhaps it is a "secret" so we should wipe it once we are
done with it.

This mirrors the logic that the audit code has.

Reported-by: aszlig <aszlig@nix.build>
Tested-by: Milan Broz <gmazyland@gmail.com>
Tested-by: Daniel Zatovic <daniel.zatovic@gmail.com>
Tested-by: aszlig <aszlig@nix.build>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Greg KH 2018-10-04 11:06:14 -07:00 committed by Greg Kroah-Hartman
parent c9a8e5fce0
commit b97b3d9fb5
1 changed files with 17 additions and 3 deletions
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20
drivers/tty/n_tty.c
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@ -152,17 +152,28 @@ static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
}
/* If we are not echoing the data, perhaps this is a secret so erase it */
static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
{
bool icanon = !!L_ICANON(tty);
bool no_echo = !L_ECHO(tty);
if (icanon && no_echo)
memset(buffer, 0x00, size);
}
static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
size_t tail, size_t n)
{
struct n_tty_data *ldata = tty->disc_data;
size_t size = N_TTY_BUF_SIZE - tail;
const void *from = read_buf_addr(ldata, tail);
void *from = read_buf_addr(ldata, tail);
int uncopied;
if (n > size) {
tty_audit_add_data(tty, from, size);
uncopied = copy_to_user(to, from, size);
zero_buffer(tty, from, size - uncopied);
if (uncopied)
return uncopied;
to += size;
@ -171,7 +182,9 @@ static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
}
tty_audit_add_data(tty, from, n);
return copy_to_user(to, from, n);
uncopied = copy_to_user(to, from, n);
zero_buffer(tty, from, n - uncopied);
return uncopied;
}
/**
@ -1960,11 +1973,12 @@ static int copy_from_read_buf(struct tty_struct *tty,
n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
n = min(*nr, n);
if (n) {
const unsigned char *from = read_buf_addr(ldata, tail);
unsigned char *from = read_buf_addr(ldata, tail);
retval = copy_to_user(*b, from, n);
n -= retval;
is_eof = n == 1 && *from == EOF_CHAR(tty);
tty_audit_add_data(tty, from, n);
zero_buffer(tty, from, n);
smp_store_release(&ldata->read_tail, ldata->read_tail + n);
/* Turn single EOF into zero-length read */
if (L_EXTPROC(tty) && ldata->icanon && is_eof &&