ipvs: reset full ip_vs_seq structs in ip_vs_conn_new

Overview

In the Linux kernel, the following vulnerability has been resolved:

ipvs: reset full ip_vs_seq structs in ip_vs_conn_new

Commit 9a05475cebdd ("ipvs: avoid kmem_cache_zalloc in ip_vs_conn_new") changed ip_vs_conn_new() to allocate an ip_vs_conn object with kmem_cache_alloc(). The function then initializes many fields explicitly, but only resets in_seq.delta and out_seq.delta in the two struct ip_vs_seq members.

That leaves init_seq and previous_delta uninitialized. This is normally harmless while the corresponding IP_VS_CONN_F_IN_SEQ or IP_VS_CONN_F_OUT_SEQ flag is clear. For connections learned from a sync message, however, ip_vs_proc_conn() preserves those flags from IP_VS_CONN_F_BACKUP_MASK and passes opt=NULL when the message omits IPVS_OPT_SEQ_DATA. In that case the new connection can be hashed with SEQ flags set but with the rest of in_seq/out_seq still containing stale slab data.

When a packet for such a connection is later handled by an IPVS application helper, vs_fix_seq() and vs_fix_ack_seq() use previous_delta and init_seq to rewrite TCP sequence numbers. A malformed sync message can therefore make forwarded packets carry stale slab bytes in their TCP seq/ack numbers, and can also corrupt the forwarded TCP flow.

Reset both struct ip_vs_seq members completely before publishing the connection. This matches the existing "reset struct ip_vs_seq" comment and keeps the sequence-adjustment gates inactive unless valid sequence data is installed later.

Affected

• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 3bf9a260188b2a5449cbddc032a749ab433fe328
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 6378c5cb360eb1750f88839d7c3613ea92ac1816
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 32c299e28b8eea6cbbd23b97dc61401e9ef9c445
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 9e36602cbec552286f7e691cfd366525c565ee74
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < d0eed7177e822cab83141e5c44b2aa345c7fd379
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 83fb4c2c5344f02eac929f66de3c9d1adfcde04c
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 6335ab62d5fc9ed875279238233fba3462c168f5
• Linux >= 9a05475cebdd6341884b5901e53870be26e65158 < 2975324d164c552b028632f107b567302863b7f6
• Linux 3.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.