Messages in this thread |  | | From | Rusty Russell <> | Subject | Re: [PATCH] lguest: explicitly setup /dev/lguest private_data | Date | Fri, 10 Apr 2015 12:58:35 +0930 |
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Greg KH <gregkh@linuxfoundation.org> writes: > On Tue, Apr 07, 2015 at 10:18:18AM +0200, Tom Van Braeckel wrote: >> The private_data member of the /dev/lguest device file is used to hold >> the current struct lguest and needs to be set to NULL to signify that >> no initialization has taken place. >> >> We explicitly set it to NULL to be independent of whatever value the >> misc subsystem initializes it to. >> >> Signed-off-by: Tom Van Braeckel <tomvanbraeckel@gmail.com> >> --- >> Backstory: >> ========== >> The misc subsystem used to initialize a file's private_data to point to >> the misc device when a driver had registered a custom open file >> operation and initialized it to NULL when a custom open file operation >> had *not* been provided. >> >> This subtle quirk was confusing, to the point where kernel code >> registered *empty* file open operations to have private_data point to >> the misc device structure. >> >> And it lead to bugs, where the addition or removal of a custom open >> file operation surprisingly changed the initial contents of a file's >> private_data structure. >> >> The misc subsystem is currently underdoing changes to *always* set >> private_data to point to the misc device instead of only doing this >> when a custom open file operation has been registered. >> >> Intel's 0day kernel testing robot discovered that the lguest driver >> depended on it implicitly being initialized to NULL, as Fengguang Wu >> reported. Thanks a lot for all the hard work! >> >> drivers/lguest/lguest_user.c | 14 +++++++++++++- >> 1 file changed, 13 insertions(+), 1 deletion(-) > > I can take this through my char-misc tree, where this misc core change > was, if the lguest maintainer (i.e. Rusty) acks it.
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cheers, Rusty.
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