CVE-2026-31546: net: bonding: fix NULL deref in bond_debug_rlb_hash_show
In the Linux kernel, the following vulnerability has been resolved:
net: bonding: fix NULL deref in bonddebugrlbhashshow
rlbclearslave intentionally keeps RLB hash-table entries on the rxhashtblusedhead list with slave set to NULL when no replacement slave is available. However, bonddebugrlbhashshow visites clientinfo->slave without checking if it's NULL.
Other used-list iterators in bondalb.c already handle this NULL-slave state safely:
- rlbupdateclient returns early on !clientinfo->slave - rlbrequpdateslaveclients, rlbclearslave, and rlbrebalance compare slave values before visiting - lbrequpdatesubnetclients continues if slave is NULL
The following NULL deref crash can be trigger in bonddebugrlbhashshow:
[ 1.289791] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 1.292058] RIP: 0010:bonddebugrlbhashshow (drivers/net/bonding/bonddebugfs.c:41) [ 1.293101] RSP: 0018:ffffc900004a7d00 EFLAGS: 00010286 [ 1.293333] RAX: 0000000000000000 RBX: ffff888102b48200 RCX: ffff888102b48204 [ 1.293631] RDX: ffff888102b48200 RSI: ffffffff839daad5 RDI: ffff888102815078 [ 1.293924] RBP: ffff888102815078 R08: ffff888102b4820e R09: 0000000000000000 [ 1.294267] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888100f929c0 [ 1.294564] R13: ffff888100f92a00 R14: 0000000000000001 R15: ffffc900004a7ed8 [ 1.294864] FS: 0000000001395380(0000) GS:ffff888196e75000(0000) knlGS:0000000000000000 [ 1.295239] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.295480] CR2: 0000000000000000 CR3: 0000000102adc004 CR4: 0000000000772ef0 [ 1.295897] Call Trace: [ 1.296134] seqreaditer (fs/seqfile.c:231) [ 1.296341] seqread (fs/seqfile.c:164) [ 1.296493] fullproxyread (fs/debugfs/file.c:378 (discriminator 1)) [ 1.296658] vfsread (fs/readwrite.c:572) [ 1.296981] ksysread (fs/readwrite.c:717) [ 1.297132] dosyscall64 (arch/x86/entry/syscall64.c:63 (discriminator 1) arch/x86/entry/syscall64.c:94 (discriminator 1)) [ 1.297325] entrySYSCALL64afterhwframe (arch/x86/entry/entry64.S:130)
Add a NULL check and print "(none)" for entries with no assigned slave.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Modify bond_debug_rlb_hash_show (drivers/net/bonding/bond_debugfs.c:41) to check whether the replacement/slave pointer (client_info->slave) is NULL before visiting it; for entries with no assigned slave, print "(none)" instead of dereferencing NULL.
Linux kernel bonding debugfs (bond_debug_rlb_hash_show in drivers/net/bonding/bond_debugfs.c) Add NULL check before dereferencing client_info->slave; print "(none)" when slave is NULL = Implement NULL check and display "(none)" for entries with no assigned slave