Messages in this thread Patch in this message |  | | From | Ben Hutchings <> | Date | Sun, 11 Feb 2018 04:20:06 +0000 | Subject | [PATCH 3.2 50/79] autofs4: catatonic_mode vs. notify_daemon race |
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3.2.99-rc1 review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@zeniv.linux.org.uk>
commit 8753333266be67ff3a984ac1f6566d31c260bee4 upstream.
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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- fs/autofs4/waitq.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-)
--- a/fs/autofs4/waitq.c +++ b/fs/autofs4/waitq.c @@ -110,6 +110,13 @@ static void autofs4_notify_daemon(struct 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 } 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); - } + 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); - } + if (autofs4_write(pipe, &pkt, pktsz)) + autofs4_catatonic_mode(sbi); + fput(pipe); } static int autofs4_getpath(struct autofs_sb_info *sbi,
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