Messages in this thread | | | Date | Thu, 11 Sep 2003 08:32:39 +0100 | From | viro@parcelfa ... | Subject | Re: Local DoS on single_open? |
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On Thu, Sep 11, 2003 at 05:26:54PM +1000, Keith Owens wrote: > On Thu, 11 Sep 2003 05:55:07 +0100, > viro@parcelfarce.linux.theplanet.co.uk wrote: > >On Thu, Sep 11, 2003 at 02:42:13PM +1000, Keith Owens wrote: > >> single_open() requires the kernel to kmalloc a buffer which lives until > >> the userspace caller closes the file. What prevents a malicious user > >> opening the same /proc entry multiple times, allocating lots of kmalloc > >> space and causing a local DoS? > > > >Size of that buffer is limited. IOW, it's not different from opening > >e.g. a shitload of pipes or sockets. > > In some cases, the buffer size is set to hold _all_ of the output for > that particular /proc file and will be much larger than the data > reserved for files and sockets. It is a difference in scale. > > fs/proc/proc_misc.c stat_open > fs/proc/proc_misc.c interrupts_open > kernel/dma.c proc_dma_open > > All those functions will kmalloc a reasonably sized buffer then let the > user control the lifetime of that buffer. Looks like a recipe for a > local DoS to me.
struct file: 256 bytes due to cacheline alignment struct dentry: 128 bytes, IIRC struct inode: either 256 bytes or 512 bytes. struct socket and struct sock: bugger if I remember, but it's not small. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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