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| author | Alan Cox <alan@lxorguk.ukuu.org.uk> | 2007-08-11 00:01:05 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-08-12 02:47:41 +0400 |
| commit | 42fd552e8647316757ded0176466c41d17934dcf (patch) | |
| tree | 07b0f4ed1934c05c6495c62ba943ab90bde6be84 /include | |
| parent | f8a745942b1b7f052cb76bb8a893d12cb6329c84 (diff) | |
| download | linux-42fd552e8647316757ded0176466c41d17934dcf.tar.xz | |
fix serial buffer memory leak
Patch c5c34d4862e18ef07c1276d233507f540fb5a532 (tty: flush flip buffer on
ldisc input queue flush) introduces a race condition which can lead to memory
leaks.
The problem can be triggered when tcflush() is called when data are being
pushed to the line discipline driver by flush_to_ldisc().
flush_to_ldisc() releases tty->buf.lock when calling the line discipline
receive_buf function. At that poing tty_buffer_flush() kicks in and sets both
tty->buf.head and tty->buf.tail to NULL. When flush_to_ldisc() finishes, it
restores tty->buf.head but doesn't touch tty->buf.tail. This corrups the
buffer queue, and the next call to tty_buffer_request_room() will allocate a
new buffer and overwrite tty->buf.head. The previous buffer is then lost
forever without being released.
(Thanks to Laurent for the above text, for finding, disgnosing and reporting
the bug)
- Use tty->flags bits for the flush status.
- Wait for the flag to clear again before returning
- Fix the doc error noted
- Fix flush of empty queue leaving stale flushpending
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Paul Fulghum <paulkf@microgate.com>
Cc: Laurent Pinchart <laurentp@cse-semaphore.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/tty.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 691a1748d9d2..6570719eafdf 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -274,6 +274,8 @@ struct tty_struct { #define TTY_PTY_LOCK 16 /* pty private */ #define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */ #define TTY_HUPPED 18 /* Post driver->hangup() */ +#define TTY_FLUSHING 19 /* Flushing to ldisc in progress */ +#define TTY_FLUSHPENDING 20 /* Queued buffer flush pending */ #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty)) |