kernel/linux.git/drivers/tty/n_tty.c, branch v6.12.80

tty: n_tty: use uint for space returned by tty_write_room()

2025-04-10T12:39:26+00:00

[ Upstream commit d97aa066678bd1e2951ee93db9690835dfe57ab6 ] tty_write_room() returns an "unsigned int". So in case some insane driver (like my tty test driver) returns (legitimate) UINT_MAX from its tty_operations::write_room(), n_tty is confused on several places. For example, in process_output_block(), the result of tty_write_room() is stored into (signed) "int". So this UINT_MAX suddenly becomes -1. And that is extended to ssize_t and returned from process_output_block(). This causes a write() to such a node to receive -EPERM (which is -1). Fix that by using proper "unsigned int" and proper "== 0" test. And return 0 constant directly in that "if", so that it is immediately clear what is returned ("space" equals to 0 at that point). Similarly for process_output() and __process_echoes(). Note this does not fix any in-tree driver as of now. If you want "Fixes: something", it would be commit 03b3b1a2405c ("tty: make tty_operations::write_room return uint"). I intentionally do not mark this patch by a real tag below. Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20250317070046.24386-6-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

tty: n_tty: Fix buffer offsets when lookahead is used

2024-06-04T12:07:27+00:00

When lookahead has "consumed" some characters (la_count > 0), n_tty_receive_buf_standard() and n_tty_receive_buf_closing() for characters beyond the la_count are given wrong cp/fp offsets which leads to duplicating and losing some characters. If la_count > 0, correct buffer pointers and make count consistent too (the latter is not strictly necessary to fix the issue but seems more logical to adjust all variables immediately to keep state consistent). Reported-by: Vadym Krevs Fixes: 6bb6fa6908eb ("tty: Implement lookahead to process XON/XOFF timely") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218834 Tested-by: Vadym Krevs Cc: stable@vger.kernel.org Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20240514140429.12087-1-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

tty: invert return values of tty_{,un}throttle_safe()

2023-10-03T12:31:15+00:00

If tty_{,un}throttle_safe() returned true on success (similar to *_trylock()), it would make the conditions in callers more obvious. So perform the switch to these inverted values (and fix the callers). Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230919085156.1578-8-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: use do-while in n_tty_check_{,un}throttle()

2023-10-03T12:31:15+00:00

This change gets rid of the complicated exit from the loops. It can be done much easier using do-while loops. Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230919085156.1578-6-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: invert the condition in copy_from_read_buf()

2023-10-03T12:31:15+00:00

Make "no numbers available" a fast quit from the function. And do the heavy work outside the 'if'. This makes the code more understandable and conforming to the common kernel coding style. Signed-off-by: "Jiri Slaby (SUSE)" Reviewed-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20230919085156.1578-5-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: use min3() in copy_from_read_buf()

2023-10-03T12:31:15+00:00

n is a minimum of: * available chars in the ring buffer * available chars in the ring buffer till the end of the ring buffer * requested number (*nr) We can use min3() for that instead of two min()s. Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230919085156.1578-4-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: rename and retype 'retval' in n_tty_ioctl()

2023-10-03T12:31:15+00:00

The value stored to the current 'retval' is number of characters. It is both obtained and put to user as unsigned. So make its type unsigned. And provided it's not a "return value" per se, rename it to 'num'. Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230919085156.1578-3-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: use 'retval' instead of 'c'

2023-10-03T12:31:15+00:00

In n_tty_read(), there is a separate int variable 'c' and is used only to hold an int value returned from job_control(). There is also a 'retval' variable typed ssize_t. So drop this single occurrence of 'c' and reuse 'retval' which is used on all other places to hold the value returned from n_tty_read(). Note that 'retval' needs not be initialized now. Drop that. Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230919085156.1578-2-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: deduplicate copy code in n_tty_receive_buf_real_raw()

2023-08-27T09:46:52+00:00

The code is duplicated to perform the copy twice -- to handle buffer wrap-around. Instead of the duplication, roll this into the loop. (And add some blank lines around to have the code a bit more readable.) Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230827074147.2287-15-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: n_tty: extract ECHO_OP processing to a separate function

2023-08-27T09:46:52+00:00

__process_echoes() contains ECHO_OPs processing. It is stuffed in a while loop and the whole function is barely readable. Separate it to a new function: n_tty_process_echo_ops(). Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20230827074147.2287-14-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman