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Both policies lack > an entry for NHA_OP_FLAGS, so the tb arrays are smaller than what > nh_valid_get_del_req() accesses via tb[NHA_OP_FLAGS]. But nh_valid_get_del_req() only accesses tb[NHA_OP_FLAGS] when 'op_flags' is not NULL and both rtm_del_nexthop() and nh_valid_get_bucket_req() pass NULL, so I don't see how this bug can happen? > > This causes an out-of-bounds stack read. The garbage pointer value > read from beyond the tb array is then dereferenced in nla_get_u32(), > triggering a NULL pointer dereference panic. > > The bug was introduced when commit 8682b7dd4f6c ("nexthop: Fix This hash doesn't exist and it differs from the one below. > out-of-bounds access during attribute validation") shrank the tb > arrays from NHA_MAX+1 to ARRAY_SIZE(policy), but the policies were > not updated to include NHA_OP_FLAGS even though nh_valid_get_del_req() > already accessed that attribute. > > Add [NHA_OP_FLAGS] entries to rtm_nh_policy_del and > rtm_nh_policy_get_bucket so the tb arrays are large enough. > > [ 647.535111] BUG: kernel NULL pointer dereference, address: 000000000000000a > [ 647.542066] #PF: supervisor read access in kernel mode > [ 647.547197] #PF: error_code(0x0000) - not-present page > [ 647.559218] CPU: 0 PID: 42929 Comm: ip Not tainted 6.6.144 #1 6.6.144 doesn't even support NHA_OP_FLAGS and doesn't have rtm_nh_policy_del. Can you reproduce the bug with net.git? > [ 647.579548] RIP: 0010:nh_valid_get_del_req+0x38/0xc0 > [ 647.998839] Kernel panic - not syncing: Fatal exception > > Fixes: d8a21070b6e1 ("nexthop: Fix out-of-bounds access during attribute validation") > Signed-off-by: Qing Luo