diff --git a/server/Cargo.lock b/server/Cargo.lock
index 2f8af8f..8692042 100644
--- a/server/Cargo.lock
+++ b/server/Cargo.lock
@@ -1062,9 +1062,9 @@ checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
 
 [[package]]
 name = "memoffset"
-version = "0.6.5"
+version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5aa361d4faea93603064a027415f07bd8e1d5c88c9fbf68bf56a285428fd79ce"
+checksum = "5de893c32cde5f383baa4c04c5d6dbdd735cfd4a794b0debdb2bb1b421da5ff4"
 dependencies = [
  "autocfg",
 ]
@@ -1260,16 +1260,16 @@ dependencies = [
 
 [[package]]
 name = "nix"
-version = "0.25.1"
+version = "0.26.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f346ff70e7dbfd675fe90590b92d59ef2de15a8779ae305ebcbfd3f0caf59be4"
+checksum = "46a58d1d356c6597d08cde02c2f09d785b09e28711837b1ed667dc652c08a694"
 dependencies = [
- "autocfg",
  "bitflags",
  "cfg-if",
  "libc",
  "memoffset",
  "pin-utils",
+ "static_assertions",
 ]
 
 [[package]]
@@ -1884,10 +1884,10 @@ dependencies = [
 ]
 
 [[package]]
-name = "sha-1"
-version = "0.10.1"
+name = "sha1"
+version = "0.10.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5058ada175748e33390e40e872bd0fe59a19f265d0158daa551c5a88a76009c"
+checksum = "f04293dc80c3993519f2d7f6f511707ee7094fe0c6d3406feb330cdb3540eba3"
 dependencies = [
  "cfg-if",
  "cpufeatures",
@@ -1961,6 +1961,12 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
+[[package]]
+name = "static_assertions"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
+
 [[package]]
 name = "structopt"
 version = "0.3.26"
@@ -2181,9 +2187,9 @@ dependencies = [
 
 [[package]]
 name = "tokio-tungstenite"
-version = "0.17.2"
+version = "0.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f714dd15bead90401d77e04243611caec13726c2408afd5b31901dfcdcb3b181"
+checksum = "54319c93411147bced34cb5609a80e0a8e44c5999c93903a81cd866630ec0bfd"
 dependencies = [
  "futures-util",
  "log",
@@ -2261,9 +2267,9 @@ checksum = "59547bce71d9c38b83d9c0e92b6066c4253371f15005def0c30d9657f50c7642"
 
 [[package]]
 name = "tungstenite"
-version = "0.17.3"
+version = "0.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e27992fd6a8c29ee7eef28fc78349aa244134e10ad447ce3b9f0ac0ed0fa4ce0"
+checksum = "30ee6ab729cd4cf0fd55218530c4522ed30b7b6081752839b68fcec8d0960788"
 dependencies = [
  "base64",
  "byteorder",
@@ -2272,7 +2278,7 @@ dependencies = [
  "httparse",
  "log",
  "rand",
- "sha-1",
+ "sha1",
  "thiserror",
  "url",
  "utf-8",
diff --git a/server/Cargo.toml b/server/Cargo.toml
index 67ab0ba..ca52ba5 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -42,7 +42,7 @@ libc = "0.2"
 log = { version = "0.4" }
 memchr = "2.0.2"
 mylog = { git = "https://github.com/scottlamb/mylog" }
-nix = "0.25.0"
+nix = "0.26.1"
 nom = "7.0.0"
 password-hash = "0.4.2"
 protobuf = "3.0"
@@ -58,7 +58,7 @@ sync_wrapper = "0.1.0"
 time = "0.1"
 tokio = { version = "1.0", features = ["macros", "rt-multi-thread", "signal", "sync", "time"] }
 tokio-stream = "0.1.5"
-tokio-tungstenite = "0.17.1"
+tokio-tungstenite = "0.18.0"
 toml = "0.5"
 tracing = { version = "0.1", features = ["log"] }
 url = "2.1.1"
diff --git a/server/db/Cargo.toml b/server/db/Cargo.toml
index 4b4c6a8..83c81c1 100644
--- a/server/db/Cargo.toml
+++ b/server/db/Cargo.toml
@@ -28,7 +28,7 @@ lazy_static = "1.0"
 libc = "0.2"
 log = "0.4"
 mylog = { git = "https://github.com/scottlamb/mylog" }
-nix = "0.25.0"
+nix = "0.26.1"
 num-rational = { version = "0.4.0", default-features = false, features = ["std"] }
 odds = { version = "0.4.0", features = ["std-vec"] }
 pretty-hex = "0.3.0"
diff --git a/server/db/dir/reader.rs b/server/db/dir/reader.rs
index a4a14f8..0214d8c 100644
--- a/server/db/dir/reader.rs
+++ b/server/db/dir/reader.rs
@@ -298,6 +298,7 @@ impl ReaderInt {
                 range
             )
         })?;
+        let map_len = std::num::NonZeroUsize::new(map_len).expect("range is non-empty");
 
         let file = crate::fs::openat(self.dir.0, &p, OFlag::O_RDONLY, Mode::empty())
             .err_kind(ErrorKind::Unknown)?;
@@ -306,7 +307,7 @@ impl ReaderInt {
         // for it to be less than the requested read. Check for this now rather than crashing
         // with a SIGBUS or reading bad data at the end of the last page later.
         let metadata = file.metadata().err_kind(ErrorKind::Unknown)?;
-        if metadata.len() < u64::try_from(offset).unwrap() + u64::try_from(map_len).unwrap() {
+        if metadata.len() < u64::try_from(offset).unwrap() + u64::try_from(map_len.get()).unwrap() {
             bail_t!(
                 Internal,
                 "file {}, range {:?}, len {}",
@@ -317,7 +318,7 @@ impl ReaderInt {
         }
         let map_ptr = unsafe {
             nix::sys::mman::mmap(
-                std::ptr::null_mut(),
+                None,
                 map_len,
                 nix::sys::mman::ProtFlags::PROT_READ,
                 nix::sys::mman::MapFlags::MAP_SHARED,
@@ -339,7 +340,7 @@ impl ReaderInt {
         if let Err(e) = unsafe {
             nix::sys::mman::madvise(
                 map_ptr as *mut libc::c_void,
-                map_len,
+                map_len.get(),
                 nix::sys::mman::MmapAdvise::MADV_SEQUENTIAL,
             )
         } {
@@ -357,7 +358,7 @@ impl ReaderInt {
             composite_id,
             map_ptr,
             map_pos: unaligned,
-            map_len,
+            map_len: map_len.get(),
         }))
     }