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packet: fix leakage of tx_ring memory
[ Upstream commit 9665d5d62487e8e7b1f546c00e11107155384b9a ] When releasing a packet socket, the routine packet_set_ring() is reused to free rings instead of allocating them. But when calling it for the first time, it fills req->tp_block_nr with the value of rb->pg_vec_len which in the second invocation makes it bail out since req->tp_block_nr is greater zero but req->tp_block_size is zero. This patch solves the problem by passing a zeroed auto-variable to packet_set_ring() upon each invocation from packet_release(). As far as I can tell, this issue exists even since 69e3c75 (net: TX_RING and packet mmap), i.e. the original inclusion of TX ring support into af_packet, but applies only to sockets with both RX and TX ring allocated, which is probably why this was unnoticed all the time. Signed-off-by: Phil Sutter <firstname.lastname@example.org> Cc: Johann Baudy <email@example.com> Cc: Daniel Borkmann <firstname.lastname@example.org> Acked-by: Daniel Borkmann <email@example.com> Signed-off-by: David S. Miller <firstname.lastname@example.org> Signed-off-by: Greg Kroah-Hartman <email@example.com>
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