bpf_xdp_shrink_data() frees a released frag via __xdp_return() using xdp->rxq->mem.type, but that type is wrong for skb-backed XDP: the skb is cow'd into page_pool memory while the rxq still says MEM_TYPE_PAGE_SHARED, so the page_pool page is freed with page_frag_free() and we hit "Bad page state ... page_pool leak". Both generic XDP and veth are affected. A non-linear skb is cow'd into page_pool memory (skb_cow_data_for_xdp() -> skb_pp_cow_data() for generic XDP, veth_convert_skb_to_xdp_buff() for veth), so its frags become page_pool pages while the rxq keeps MEM_TYPE_PAGE_SHARED. We can't just fix rxq->mem.type in place: - generic XDP: xdp->rxq is dev->_rx[queue].xdp_rxq (see bpf_prog_run_generic_xdp()), a shared rxq that other CPUs may access in parallel, so we must not write to it. - veth: rq->xdp_rxq.mem is shared per-queue state that veth resets on XDP teardown, and with GRO that reset runs without stopping in-flight NAPI, so a type stashed there can be clobbered under a packet still in flight. Adding a check in __xdp_return() or bpf_xdp_shrink_data() itself is not an option either: without recording it somewhere, both can only guess the frag's memory type, which quickly gets confusing. So record it in the xdp_buff. A dedicated mem_type field (mirroring xdp_frame->mem_type) would read more naturally, but it grows xdp_buff, and struct xdp_page_head embeds two of them, which shifts the layout the xdp_do_redirect live-frames selftest hard-codes (MAX_PKT_SIZE). So use a flag bit: add XDP_FLAGS_FRAGS_PAGE_POOL, the two skb-cow sites set it, and bpf_xdp_shrink_data() frees the frag to the page_pool when it is set, otherwise it keeps falling back to xdp->rxq->mem.type unchanged. The flag describes the buff, so the buff <-> frame conversions have to keep it consistent: - buff -> frame: xdp_update_frame_from_buff() copies xdp->flags into the frame. veth XDP_TX/XDP_REDIRECT hand the frame to the peer, and cpumap and devmap run a second program on it, so the peer would inherit a stale tag; strip it, an xdp_frame describes its memory with ::mem_type. - frame -> buff: xdp_convert_frame_to_buff() rebuilds a buff, and veth and devmap then run a program whose rxq says MEM_TYPE_PAGE_SHARED even for a page_pool frame (only cpumap copies mem_type into the rxq). A shrink there leaks the same way (this predates the series: bpf_xdp_adjust_tail() frees frags by rxq->mem.type), so re-derive the flag from the frame's ::mem_type. Fixes: e6d5dbdd20aa ("xdp: add multi-buff support for xdp running in generic mode") Fixes: 0ebab78cbcbf ("net: veth: add page_pool for page recycling") Fixes: bf25146a5595 ("bpf: add frags support to the bpf_xdp_adjust_tail() API") Reported-by: syzbot+237bbeed8dfe0699b7f5@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=237bbeed8dfe0699b7f5 Signed-off-by: Jiayuan Chen --- drivers/net/veth.c | 6 ++++++ include/net/xdp.h | 30 +++++++++++++++++++++++++++++- net/core/dev.c | 6 ++++++ net/core/filter.c | 7 +++++++ 4 files changed, 48 insertions(+), 1 deletion(-) diff --git a/drivers/net/veth.c b/drivers/net/veth.c index 6ed3ee81153fb..a3fdf1959b76c 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -775,6 +775,12 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq, if (skb_shinfo(skb)->nr_frags) { skb_shinfo(skb)->xdp_frags_size = skb->data_len; xdp_buff_set_frags_flag(xdp); + /* + * A nonlinear skb was cow'd into rq->page_pool above, so the + * frags must be freed to that pool, not via the rxq's + * MEM_TYPE_PAGE_SHARED. + */ + xdp_buff_set_frag_pp(xdp); } else { xdp_buff_clear_frags_flag(xdp); } diff --git a/include/net/xdp.h b/include/net/xdp.h index aa742f413c358..8fd4139e9cbd3 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -81,6 +81,14 @@ enum xdp_buff_flags { * XDP program is not attached. */ XDP_FLAGS_FRAGS_UNREADABLE = BIT(2), + /* + * frags are page_pool memory even though rxq->mem.type is not: a + * skb-backed XDP buff (generic XDP, veth) is cow'd into a page_pool. + * xdp_buff only: an xdp_frame describes its memory with ::mem_type, so + * this is stripped in xdp_update_frame_from_buff() and re-derived from + * ::mem_type in xdp_convert_frame_to_buff(). + */ + XDP_FLAGS_FRAGS_PAGE_POOL = BIT(3), }; struct xdp_buff { @@ -131,6 +139,16 @@ static __always_inline void xdp_buff_set_frag_unreadable(struct xdp_buff *xdp) xdp->flags |= XDP_FLAGS_FRAGS_UNREADABLE; } +static __always_inline void xdp_buff_set_frag_pp(struct xdp_buff *xdp) +{ + xdp->flags |= XDP_FLAGS_FRAGS_PAGE_POOL; +} + +static __always_inline bool xdp_buff_is_frag_pp(const struct xdp_buff *xdp) +{ + return !!(xdp->flags & XDP_FLAGS_FRAGS_PAGE_POOL); +} + static __always_inline u32 xdp_buff_get_skb_flags(const struct xdp_buff *xdp) { return xdp->flags; @@ -394,6 +412,15 @@ void xdp_convert_frame_to_buff(const struct xdp_frame *frame, xdp->data_meta = frame->data - frame->metasize; xdp->frame_sz = frame->frame_sz; xdp->flags = frame->flags; + /* + * frame->flags never carries XDP_FLAGS_FRAGS_PAGE_POOL (it is stripped + * in xdp_update_frame_from_buff()); re-derive it from the frame's own + * memory type. veth and devmap rebuild a buff here and run a program + * whose rxq says MEM_TYPE_PAGE_SHARED, so without this a shrink would + * free a page_pool frag through page_frag_free(). + */ + if (frame->mem_type == MEM_TYPE_PAGE_POOL) + xdp_buff_set_frag_pp(xdp); } static inline @@ -420,7 +447,8 @@ int xdp_update_frame_from_buff(const struct xdp_buff *xdp, xdp_frame->headroom = headroom - sizeof(*xdp_frame); xdp_frame->metasize = metasize; xdp_frame->frame_sz = xdp->frame_sz; - xdp_frame->flags = xdp->flags; + /* XDP_FLAGS_FRAGS_PAGE_POOL is xdp_buff only, don't carry it over */ + xdp_frame->flags = xdp->flags & ~XDP_FLAGS_FRAGS_PAGE_POOL; return 0; } diff --git a/net/core/dev.c b/net/core/dev.c index 290e0f099e6bf..94268f4d3c5f7 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5532,6 +5532,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, if (skb_is_nonlinear(skb)) { skb_shinfo(skb)->xdp_frags_size = skb->data_len; xdp_buff_set_frags_flag(xdp); + /* + * A nonlinear skb was cow'd into page_pool memory by + * skb_cow_data_for_xdp() before we got here, so the frags must + * be freed to that pool, not via the rxq's MEM_TYPE_PAGE_SHARED. + */ + xdp_buff_set_frag_pp(xdp); } else { xdp_buff_clear_frags_flag(xdp); } diff --git a/net/core/filter.c b/net/core/filter.c index 61940e7535523..d34ba56d79d8f 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4378,6 +4378,13 @@ static bool bpf_xdp_shrink_data(struct xdp_buff *xdp, skb_frag_t *frag, if (mem_type == MEM_TYPE_XSK_BUFF_POOL) { netmem = 0; zc_frag = bpf_xdp_shrink_data_zc(xdp, shrink, tail, release); + } else if (xdp_buff_is_frag_pp(xdp)) { + /* + * Skb-backed XDP (generic XDP, veth) cow's the frags into a + * page_pool while the rxq stays MEM_TYPE_PAGE_SHARED, so free + * the frag to the pool, not via page_frag_free(). + */ + mem_type = MEM_TYPE_PAGE_POOL; } if (release) { -- 2.43.0