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xen-netback: fix debugfs write length check
Enlarge buffer size and check input length properly, so that we don't misuse -ENOSPC. Note that command like "kickXXXX" is still allowed, that's one patch for another day if we really want to be very strict on this. Reported-by: SeeChen Ng <seechen81@gmail.com> Signed-off-by: Wei Liu <wei.liu2@citrix.com> Cc: Zoltan Kiss <zoltan.kiss@citrix.com> Cc: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -116,6 +116,7 @@ static int xenvif_read_io_ring(struct seq_file *m, void *v)
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}
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#define XENVIF_KICK_STR "kick"
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#define BUFFER_SIZE 32
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static ssize_t
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xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count,
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@ -124,22 +125,24 @@ xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count,
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struct xenvif_queue *queue =
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((struct seq_file *)filp->private_data)->private;
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int len;
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char write[sizeof(XENVIF_KICK_STR)];
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char write[BUFFER_SIZE];
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/* don't allow partial writes and check the length */
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if (*ppos != 0)
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return 0;
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if (count < sizeof(XENVIF_KICK_STR) - 1)
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if (count >= sizeof(write))
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return -ENOSPC;
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len = simple_write_to_buffer(write,
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sizeof(write),
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sizeof(write) - 1,
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ppos,
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buf,
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count);
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if (len < 0)
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return len;
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write[len] = '\0';
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if (!strncmp(write, XENVIF_KICK_STR, sizeof(XENVIF_KICK_STR) - 1))
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xenvif_interrupt(0, (void *)queue);
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else {
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