Hi! > From: Vivien Didelot <vivien.didelot@xxxxxxxxx> > > [ Upstream commit 0ee4e76937d69128a6a66861ba393ebdc2ffc8a2 ] > > ethtool_get_regs() allocates a buffer of size ops->get_regs_len(), > and pass it to the kernel driver via ops->get_regs() for filling. > > There is no restriction about what the kernel drivers can or cannot do > with the open ethtool_regs structure. They usually set regs->version > and ignore regs->len or set it to the same size as ops->get_regs_len(). > > But if userspace allocates a smaller buffer for the registers dump, > we would cause a userspace buffer overflow in the final copy_to_user() > call, which uses the regs.len value potentially reset by the driver. > > To fix this, make this case obvious and store regs.len before calling > ops->get_regs(), to only copy as much data as requested by userspace, > up to the value returned by ops->get_regs_len(). > > While at it, remove the redundant check for non-null regbuf. Mainline differs from 4.19-stable here, and while the non-null check is redundant in -mainline, it does not seem to be redundant in -stable. In stable, if get_regs_len() returns < 0, we'll pass it to vzalloc. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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