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[PATCH] tty: ->signal->tty locking

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Fix the locking of signal->tty.

Use ->sighand->siglock to protect ->signal->tty; this lock is already used
by most other members of ->signal/->sighand.  And unless we are 'current'
or the tasklist_lock is held we need ->siglock to access ->signal anyway.

(NOTE: sys_unshare() is broken wrt ->sighand locking rules)

Note that tty_mutex is held over tty destruction, so while holding
tty_mutex any tty pointer remains valid.  Otherwise the lifetime of ttys
are governed by their open file handles.  This leaves some holes for tty
access from signal->tty (or any other non file related tty access).

It solves the tty SLAB scribbles we were seeing.

(NOTE: the change from group_send_sig_info to __group_send_sig_info needs to
       be examined by someone familiar with the security framework, I think
       it is safe given the SEND_SIG_PRIV from other __group_send_sig_info
       invocations)

[schwidefsky@de.ibm.com: 3270 fix]
[akpm@osdl.org: various post-viro fixes]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Alan Cox <alan@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Jan Kara <jack@ucw.cz>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Peter Zijlstra
2006-12-08 02:36:04 -08:00
committed by Linus Torvalds
parent 562f9c574e
commit 24ec839c43
12 changed files with 186 additions and 132 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
fs/dquot.c
View File

@@ -828,6 +828,7 @@ static inline int need_print_warning(struct dquot *dquot)
static void print_warning(struct dquot *dquot, const char warntype)
{
char *msg = NULL;
struct tty_struct *tty;
int flag = (warntype == BHARDWARN || warntype == BSOFTLONGWARN) ? DQ_BLKS_B :
((warntype == IHARDWARN || warntype == ISOFTLONGWARN) ? DQ_INODES_B : 0);
@@ -835,14 +836,15 @@ static void print_warning(struct dquot *dquot, const char warntype)
return;
mutex_lock(&tty_mutex);
if (!current->signal->tty)
tty = get_current_tty();
if (!tty)
goto out_lock;
tty_write_message(current->signal->tty, dquot->dq_sb->s_id);
tty_write_message(tty, dquot->dq_sb->s_id);
if (warntype == ISOFTWARN || warntype == BSOFTWARN)
tty_write_message(current->signal->tty, ": warning, ");
tty_write_message(tty, ": warning, ");
else
tty_write_message(current->signal->tty, ": write failed, ");
tty_write_message(current->signal->tty, quotatypes[dquot->dq_type]);
tty_write_message(tty, ": write failed, ");
tty_write_message(tty, quotatypes[dquot->dq_type]);
switch (warntype) {
case IHARDWARN:
msg = " file limit reached.\r\n";
@@ -863,7 +865,7 @@ static void print_warning(struct dquot *dquot, const char warntype)
msg = " block quota exceeded.\r\n";
break;
}
tty_write_message(current->signal->tty, msg);
tty_write_message(tty, msg);
out_lock:
mutex_unlock(&tty_mutex);
}