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autofs4: catatonic_mode vs. notify_daemon race

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we need to hold ->wq_mutex while we are forming the packet to send,
lest we have autofs4_catatonic_mode() setting wq->name.name to NULL
just as autofs4_notify_daemon() decides to memcpy() from it...

We do have check for catatonic mode immediately after that (under
->wq_mutex, as it ought to be) and packet won't be actually sent,
but it'll be too late for us if we oops on that memcpy() from NULL...

Fix is obvious - just extend the area covered by ->wq_mutex over
that switch and check whether it's catatonic *before* doing anything
else.

Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2012-01-10 22:24:48 -05:00
parent 4041bcdc7b
commit 8753333266
1 changed files with 14 additions and 11 deletions
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15
fs/autofs4/waitq.c
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@ -110,6 +110,13 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
pkt.hdr.proto_version = sbi->version;
pkt.hdr.type = type;
mutex_lock(&sbi->wq_mutex);
/* Check if we have become catatonic */
if (sbi->catatonic) {
mutex_unlock(&sbi->wq_mutex);
return;
}
switch (type) {
/* Kernel protocol v4 missing and expire packets */
case autofs_ptype_missing:
@ -163,22 +170,18 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
}
default:
printk("autofs4_notify_daemon: bad type %d!\n", type);
mutex_unlock(&sbi->wq_mutex);
return;
}
/* Check if we have become catatonic */
mutex_lock(&sbi->wq_mutex);
if (!sbi->catatonic) {
pipe = sbi->pipe;
get_file(pipe);
}
mutex_unlock(&sbi->wq_mutex);
if (pipe) {
if (autofs4_write(pipe, &pkt, pktsz))
autofs4_catatonic_mode(sbi);
fput(pipe);
}
}
static int autofs4_getpath(struct autofs_sb_info *sbi,