Andrew Lukoshko
63cf6080c5
rxrpc: linearize incoming DATA packet when it has paged frags Sibling fix to the xfrm/esp patch shipped in 124.55.2. rxrpc.ko is built but shipped only via kernel-modules-partner; users who install that subpackage are exposed without this fix.
69 lines
2.5 KiB
Diff
69 lines
2.5 KiB
Diff
From: Andrew Lukoshko <alukoshko@almalinux.org>
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Subject: [PATCH AlmaLinux 10] rxrpc: linearize incoming DATA packet when it has paged frags
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AlmaLinux-specific backport of the intent of the upstream rxrpc fix
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posted at https://lore.kernel.org/all/afKV2zGR6rrelPC7@v4bel/
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(sibling to upstream commit f4c50a4034e6 in the ESP/xfrm subsystem).
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The upstream patch can not be cherry-picked against this 6.12 tree:
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its target lines were introduced by upstream commit d0d5c0cd1e71
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("rxrpc: Use skb_unshare() rather than skb_cow_data()") which is not
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present here. The age-equivalent code path on AlmaLinux 10 is the
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centralized skb_unshare() in net/rxrpc/io_thread.c that is run for
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every DATA packet with a non-zero securityIndex before in-place
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decryption.
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skb_unshare() only handles cloned skbs. An skb that is non-cloned but
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carries paged fragments (skb->data_len != 0) — e.g. pages attached via
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udp_sendpage() / splice() / MSG_SPLICE_PAGES on a UDP socket carrying
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rxrpc traffic — slips through and is decrypted in place over data the
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skb does not own privately. With kernel-modules-partner installed
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(rxrpc.ko enabled), this is exploitable.
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Replace the unconditional skb_unshare() with skb_copy() whenever the
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skb is cloned OR carries paged fragments. skb_copy() always returns a
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freshly allocated linear skb, so subsequent in-place decryption only
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touches kernel-owned memory. The original skb is consumed explicitly
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(skb_unshare did this internally via consume_skb()).
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Verified to apply with `patch -p1 -F0` (no offset, no fuzz, no
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rejects) against kernel-6.12.0-124.55.1.el10_1.
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Fixes: cac2661c53f3 ("rxrpc: Use skb_cow_data() in rxrpc_recvmsg_data()")
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Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
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---
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net/rxrpc/io_thread.c | 18 ++++++++++--------
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1 file changed, 10 insertions(+), 8 deletions(-)
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--- a/net/rxrpc/io_thread.c
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+++ b/net/rxrpc/io_thread.c
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@@ -235,16 +235,18 @@
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* decryption.
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*/
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if (sp->hdr.securityIndex != 0) {
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- skb = skb_unshare(skb, GFP_ATOMIC);
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- if (!skb) {
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- rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare_nomem);
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- *_skb = NULL;
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- return just_discard;
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- }
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+ if (skb_cloned(skb) || skb->data_len) {
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+ struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
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+
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+ if (!nskb) {
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+ rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare_nomem);
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+ return just_discard;
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+ }
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- if (skb != *_skb) {
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rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare);
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- *_skb = skb;
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+ consume_skb(*_skb);
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+ *_skb = nskb;
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+ skb = nskb;
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rxrpc_new_skb(skb, rxrpc_skb_new_unshared);
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sp = rxrpc_skb(skb);
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}
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--
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2.43.0
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