| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.12 115/212] n_tty: Fix 4096-byte canonical reads | Date | Mon, 2 Dec 2013 11:15:06 -0800 |
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3.12-stable review patch. If anyone has any objections, please let me know.
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From: Peter Hurley <peter@hurleysoftware.com>
commit c77569d2f3ef7844ee4ac7005a57da6898b302a8 upstream.
Although the maximum allowable canonical line is specified to be 255 bytes (MAX_CANON), the practical limit has actually been the size of the line discipline read buffer (N_TTY_BUF_SIZE == 4096).
Commit 32f13521ca68bc624ff6effc77f308a52b038bf0, n_tty: Line copy to user buffer in canonical mode, limited the line copy to 4095 bytes. With a completely full line discipline read buffer and a userspace buffer > 4095, _no_ data was copied, and the read() syscall returned 0, indicating EOF.
Fix the interval arithmetic to compute the correct number of bytes to copy to userspace in the range [1..4096].
Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/tty/n_tty.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2005,7 +2005,10 @@ static int canon_copy_from_read_buf(stru found = 1; size = N_TTY_BUF_SIZE - tail; - n = (found + eol + size) & (N_TTY_BUF_SIZE - 1); + n = eol - tail; + if (n > 4096) + n += 4096; + n += found; c = n; if (found && read_buf(ldata, eol) == __DISABLED_CHAR) {
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