Commit dfccd0f5 authored by Samuel Ortiz's avatar Samuel Ortiz

NFC: pn533: Add some polling entropy

By not always starting the polling loop from the same modulation, we
avoid entering infinite loops where devices exporting 2 targets (on 2
different modulations) get the same target activated over and over.
If this target is not readable (e.g. a wallet emulating a tag), we will
stay in an error loop for ever.
Signed-off-by: default avatarSamuel Ortiz <sameo@linux.intel.com>
parent 46f793b0
...@@ -1913,6 +1913,7 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev, ...@@ -1913,6 +1913,7 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev,
u32 im_protocols, u32 tm_protocols) u32 im_protocols, u32 tm_protocols)
{ {
struct pn533 *dev = nfc_get_drvdata(nfc_dev); struct pn533 *dev = nfc_get_drvdata(nfc_dev);
u8 rand_mod;
nfc_dev_dbg(&dev->interface->dev, nfc_dev_dbg(&dev->interface->dev,
"%s: im protocols 0x%x tm protocols 0x%x", "%s: im protocols 0x%x tm protocols 0x%x",
...@@ -1936,11 +1937,15 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev, ...@@ -1936,11 +1937,15 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev,
tm_protocols = 0; tm_protocols = 0;
} }
dev->poll_mod_curr = 0;
pn533_poll_create_mod_list(dev, im_protocols, tm_protocols); pn533_poll_create_mod_list(dev, im_protocols, tm_protocols);
dev->poll_protocols = im_protocols; dev->poll_protocols = im_protocols;
dev->listen_protocols = tm_protocols; dev->listen_protocols = tm_protocols;
/* Do not always start polling from the same modulation */
get_random_bytes(&rand_mod, sizeof(rand_mod));
rand_mod %= dev->poll_mod_count;
dev->poll_mod_curr = rand_mod;
return pn533_send_poll_frame(dev); return pn533_send_poll_frame(dev);
} }
......
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