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979990c628
kernelci.org reports a crazy stack usage for the VT code when CONFIG_KASAN
is enabled:
drivers/tty/vt/keyboard.c: In function 'kbd_keycode':
drivers/tty/vt/keyboard.c:1452:1: error: the frame size of 2240 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
The problem is that tty_insert_flip_char() gets inlined many times into
kbd_keycode(), and also into other functions, and each copy requires 128
bytes for stack redzone to check for a possible out-of-bounds access on
the 'ch' and 'flags' arguments that are passed into
tty_insert_flip_string_flags as a variable-length string.
This introduces a new __tty_insert_flip_char() function for the slow
path, which receives the two arguments by value. This completely avoids
the problem and the stack usage goes back down to around 100 bytes.
Without KASAN, this is also slightly better, as we don't have to
spill the arguments to the stack but can simply pass 'ch' and 'flag'
in registers, saving a few bytes in .text for each call site.
This should be backported to linux-4.0 or later, which first introduced
the stack sanitizer in the kernel.
Cc: stable@vger.kernel.org
Fixes: c420f167db ("kasan: enable stack instrumentation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
43 lines
1.5 KiB
C
43 lines
1.5 KiB
C
#ifndef _LINUX_TTY_FLIP_H
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#define _LINUX_TTY_FLIP_H
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extern int tty_buffer_set_limit(struct tty_port *port, int limit);
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extern int tty_buffer_space_avail(struct tty_port *port);
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extern int tty_buffer_request_room(struct tty_port *port, size_t size);
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extern int tty_insert_flip_string_flags(struct tty_port *port,
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const unsigned char *chars, const char *flags, size_t size);
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extern int tty_insert_flip_string_fixed_flag(struct tty_port *port,
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const unsigned char *chars, char flag, size_t size);
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extern int tty_prepare_flip_string(struct tty_port *port,
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unsigned char **chars, size_t size);
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extern void tty_flip_buffer_push(struct tty_port *port);
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void tty_schedule_flip(struct tty_port *port);
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int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag);
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static inline int tty_insert_flip_char(struct tty_port *port,
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unsigned char ch, char flag)
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{
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struct tty_buffer *tb = port->buf.tail;
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int change;
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change = (tb->flags & TTYB_NORMAL) && (flag != TTY_NORMAL);
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if (!change && tb->used < tb->size) {
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if (~tb->flags & TTYB_NORMAL)
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*flag_buf_ptr(tb, tb->used) = flag;
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*char_buf_ptr(tb, tb->used++) = ch;
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return 1;
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}
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return __tty_insert_flip_char(port, ch, flag);
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}
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static inline int tty_insert_flip_string(struct tty_port *port,
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const unsigned char *chars, size_t size)
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{
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return tty_insert_flip_string_fixed_flag(port, chars, TTY_NORMAL, size);
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}
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extern void tty_buffer_lock_exclusive(struct tty_port *port);
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extern void tty_buffer_unlock_exclusive(struct tty_port *port);
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#endif /* _LINUX_TTY_FLIP_H */
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