4.19-stable review patch. If anyone has any objections, please let me know.
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From: Greg Kroah-Hartman greg@kroah.com
commit b97b3d9fb57860a60592859e332de7759fd54c2e upstream.
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
--- drivers/tty/n_tty.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)
--- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -152,17 +152,28 @@ static inline unsigned char *echo_buf_ad 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_s }
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 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 &&