sentry/fuse: validate NodeID in LOOKUP responses#13525
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The NodeID validation (reject 0 and FUSE_ROOT_ID) was gated behind opcode != FUSE_LOOKUP, so LOOKUP responses from the FUSE daemon bypassed all NodeID checks. A malicious daemon could return NodeID=0 (which means "no such entry" in the FUSE protocol) and gVisor would create a real inode with that ID, or return FUSE_ROOT_ID to create inode aliasing with the root. Split the validation so that NodeID checks apply to all response types. For LOOKUP with NodeID=0, return ENOENT (matching Linux fuse_lookup_name behavior for negative lookups). For FUSE_ROOT_ID or NodeID=0 on non-LOOKUP opcodes, return EIO. File type validation remains LOOKUP-exempt since LOOKUP doesn't pass an expected type.
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The NodeID validation (reject 0 and FUSE_ROOT_ID) in newEntry was gated behind `opcode != linux.FUSE_LOOKUP`, so LOOKUP responses from the FUSE daemon bypassed all NodeID checks. A FUSE daemon could return NodeID=0 (which means "no such entry" in the FUSE protocol) and gVisor would create a real inode with that ID, or return FUSE_ROOT_ID to alias the root inode. This splits the validation so that NodeID checks apply to all response types. For LOOKUP with NodeID=0, returns ENOENT to match Linux `fuse_lookup_name()` behavior for negative lookups. For FUSE_ROOT_ID or NodeID=0 on non-LOOKUP opcodes, returns EIO. File type validation remains LOOKUP-exempt since LOOKUP doesn't pass an expected type. FUTURE_COPYBARA_INTEGRATE_REVIEW=#13525 from TristanInSec:fix-fuse-lookup-nodeid-validation f4f4837 PiperOrigin-RevId: 944063075
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The NodeID validation (reject 0 and FUSE_ROOT_ID) in newEntry was gated behind
opcode != linux.FUSE_LOOKUP, so LOOKUP responses from the FUSE daemon bypassed all NodeID checks. A FUSE daemon could return NodeID=0 (which means "no such entry" in the FUSE protocol) and gVisor would create a real inode with that ID, or return FUSE_ROOT_ID to alias the root inode.This splits the validation so that NodeID checks apply to all response types. For LOOKUP with NodeID=0, returns ENOENT to match Linux
fuse_lookup_name()behavior for negative lookups. For FUSE_ROOT_ID or NodeID=0 on non-LOOKUP opcodes, returns EIO. File type validation remains LOOKUP-exempt since LOOKUP doesn't pass an expected type.