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Eric Dumazet 543adf0721 ppp: annotate data races in ppp_generic ...

Several fields in struct ppp can be read or updated concurrently
from multiple CPUs without synchronization, causing data races:

1. ppp->mru is read concurrently in ppp_receive_nonmp_frame() while
   being updated via PPPIOCSMRU ioctl. Protect ppp->mru updates in
   PPPIOCSMRU with ppp_recv_lock(ppp).

2. PPPIOCGFLAGS reads ppp->flags, ppp->xstate, and ppp->rstate
   unlocked. Wrap the read in ppp_lock(ppp) to get a consistent
   snapshot.

3. ppp->debug is updated via PPPIOCSDEBUG and read concurrently on
   fast paths. Annotate reads with READ_ONCE() and writes with
   WRITE_ONCE().

4. ppp->last_xmit and ppp->last_recv are updated on TX/RX data paths
   and read via PPPIOCGIDLE32 / PPPIOCGIDLE64 ioctls. Annotate with
   WRITE_ONCE() / READ_ONCE() and use max() to handle jiffies
   subtraction.

5. ppp->npmode[] is updated via PPPIOCSNPMODE and read on TX/RX
   paths. Annotate with WRITE_ONCE() / READ_ONCE().

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Qingfang Deng <qingfang.deng@linux.dev>
Link: https://patch.msgid.link/20260722101605.2868548-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2026-07-23 07:01:37 -07:00

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