6.12-stable review patch. If anyone has any objections, please let me know.
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From: Alexander Lobakin aleksander.lobakin@intel.com
commit 07ca98f906a403637fc5e513a872a50ef1247f3b upstream.
Turned out certain clearly invalid values passed in xdp_desc from userspace can pass xp_{,un}aligned_validate_desc() and then lead to UBs or just invalid frames to be queued for xmit.
desc->len close to ``U32_MAX`` with a non-zero pool->tx_metadata_len can cause positive integer overflow and wraparound, the same way low enough desc->addr with a non-zero pool->tx_metadata_len can cause negative integer overflow. Both scenarios can then pass the validation successfully. This doesn't happen with valid XSk applications, but can be used to perform attacks.
Always promote desc->len to ``u64`` first to exclude positive overflows of it. Use explicit check_{add,sub}_overflow() when validating desc->addr (which is ``u64`` already).
bloat-o-meter reports a little growth of the code size:
add/remove: 0/0 grow/shrink: 2/1 up/down: 60/-16 (44) Function old new delta xskq_cons_peek_desc 299 330 +31 xsk_tx_peek_release_desc_batch 973 1002 +29 xsk_generic_xmit 3148 3132 -16
but hopefully this doesn't hurt the performance much.
Fixes: 341ac980eab9 ("xsk: Support tx_metadata_len") Cc: stable@vger.kernel.org # 6.8+ Signed-off-by: Alexander Lobakin aleksander.lobakin@intel.com Reviewed-by: Jason Xing kerneljasonxing@gmail.com Reviewed-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Link: https://lore.kernel.org/r/20251008165659.4141318-1-aleksander.lobakin@intel.... Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/xdp/xsk_queue.h | 45 +++++++++++++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 10 deletions(-)
--- a/net/xdp/xsk_queue.h +++ b/net/xdp/xsk_queue.h @@ -143,14 +143,24 @@ static inline bool xp_unused_options_set static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc) { - u64 addr = desc->addr - pool->tx_metadata_len; - u64 len = desc->len + pool->tx_metadata_len; - u64 offset = addr & (pool->chunk_size - 1); + u64 len = desc->len; + u64 addr, offset;
- if (!desc->len) + if (!len) return false;
- if (offset + len > pool->chunk_size) + /* Can overflow if desc->addr < pool->tx_metadata_len */ + if (check_sub_overflow(desc->addr, pool->tx_metadata_len, &addr)) + return false; + + offset = addr & (pool->chunk_size - 1); + + /* + * Can't overflow: @offset is guaranteed to be < ``U32_MAX`` + * (pool->chunk_size is ``u32``), @len is guaranteed + * to be <= ``U32_MAX``. + */ + if (offset + len + pool->tx_metadata_len > pool->chunk_size) return false;
if (addr >= pool->addrs_cnt) @@ -158,27 +168,42 @@ static inline bool xp_aligned_validate_d
if (xp_unused_options_set(desc->options)) return false; + return true; }
static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc) { - u64 addr = xp_unaligned_add_offset_to_addr(desc->addr) - pool->tx_metadata_len; - u64 len = desc->len + pool->tx_metadata_len; + u64 len = desc->len; + u64 addr, end;
- if (!desc->len) + if (!len) return false;
+ /* Can't overflow: @len is guaranteed to be <= ``U32_MAX`` */ + len += pool->tx_metadata_len; if (len > pool->chunk_size) return false;
- if (addr >= pool->addrs_cnt || addr + len > pool->addrs_cnt || - xp_desc_crosses_non_contig_pg(pool, addr, len)) + /* Can overflow if desc->addr is close to 0 */ + if (check_sub_overflow(xp_unaligned_add_offset_to_addr(desc->addr), + pool->tx_metadata_len, &addr)) + return false; + + if (addr >= pool->addrs_cnt) + return false; + + /* Can overflow if pool->addrs_cnt is high enough */ + if (check_add_overflow(addr, len, &end) || end > pool->addrs_cnt) + return false; + + if (xp_desc_crosses_non_contig_pg(pool, addr, len)) return false;
if (xp_unused_options_set(desc->options)) return false; + return true; }