sane blksize to avoid memory kill in split -n 3 /dev/zero

src/uu/head/src/head.rs

@@ -7,10 +7,7 @@
 
 use clap::{crate_version, Arg, ArgAction, ArgMatches, Command};
 use std::ffi::OsString;
-use std::fs::Metadata;
 use std::io::{self, BufWriter, ErrorKind, Read, Seek, SeekFrom, Write};
-#[cfg(not(target_os = "windows"))]
-use std::os::unix::fs::MetadataExt;
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult, USimpleError};
 use uucore::line_ending::LineEnding;
@@ -401,30 +398,10 @@ fn is_seekable(input: &mut std::fs::File) -> bool {
         && input.seek(SeekFrom::Start(current_pos.unwrap())).is_ok()
 }
 
-fn sanity_limited_blksize(_st: &Metadata) -> u64 {
-    #[cfg(not(target_os = "windows"))]
-    {
-        const DEFAULT: u64 = 512;
-        const MAX: u64 = usize::MAX as u64 / 8 + 1;
-
-        let st_blksize: u64 = _st.blksize();
-        match st_blksize {
-            0 => DEFAULT,
-            1..=MAX => st_blksize,
-            _ => DEFAULT,
-        }
-    }
-
-    #[cfg(target_os = "windows")]
-    {
-        512
-    }
-}
-
 fn head_backwards_file(input: &mut std::fs::File, options: &HeadOptions) -> std::io::Result<()> {
     let st = input.metadata()?;
     let seekable = is_seekable(input);
-    let blksize_limit = sanity_limited_blksize(&st);
+    let blksize_limit = uucore::fs::sane_blksize::sane_blksize_from_metadata(&st);
     if !seekable || st.len() <= blksize_limit {
         return head_backwards_without_seek_file(input, options);
     }

src/uu/split/src/split.rs

@@ -43,18 +43,6 @@ static OPT_VERBOSE: &str = "verbose";
 static OPT_SEPARATOR: &str = "separator";
 static OPT_ELIDE_EMPTY_FILES: &str = "elide-empty-files";
 static OPT_IO_BLKSIZE: &str = "-io-blksize";
-// Cap ---io-blksize value
-// For 64bit systems the max value is the same as in GNU
-// and is equivalent of `i32::MAX >> 20 << 20` operation.
-// On 32bit systems however, even though it fits within `u32` and `i32`,
-// it causes rust-lang `library/alloc/src/raw_vec.rs` to panic with 'capacity overflow' error.
-// Could be due to how `std::io::BufReader` handles internal buffers.
-// So we use much smaller value for those
-static OPT_IO_BLKSIZE_MAX: usize = if usize::BITS >= 64 {
-    2_146_435_072
-} else {
-    1_000_000_000
-};
 
 static ARG_INPUT: &str = "input";
 static ARG_PREFIX: &str = "prefix";
@@ -421,7 +409,7 @@ struct Settings {
     /// chunks. If this is `false`, then empty files will not be
     /// created.
     elide_empty_files: bool,
-    io_blksize: Option<usize>,
+    io_blksize: Option<u64>,
 }
 
 /// An error when parsing settings from command-line arguments.
@@ -512,17 +500,10 @@ impl Settings {
             None => b'\n',
         };
 
-        let io_blksize: Option<usize> = if let Some(s) = matches.get_one::<String>(OPT_IO_BLKSIZE) {
+        let io_blksize: Option<u64> = if let Some(s) = matches.get_one::<String>(OPT_IO_BLKSIZE) {
             match parse_size_u64(s) {
-                Ok(n) => {
-                    let n: usize = n
-                        .try_into()
-                        .map_err(|_| SettingsError::InvalidIOBlockSize(s.to_string()))?;
-                    if n > OPT_IO_BLKSIZE_MAX {
-                        return Err(SettingsError::InvalidIOBlockSize(s.to_string()));
-                    }
-                    Some(n)
-                }
+                Ok(0) => return Err(SettingsError::InvalidIOBlockSize(s.to_string())),
+                Ok(n) if n <= uucore::fs::sane_blksize::MAX => Some(n),
                 _ => return Err(SettingsError::InvalidIOBlockSize(s.to_string())),
             }
         } else {
@@ -645,14 +626,18 @@ fn get_input_size<R>(
     input: &String,
     reader: &mut R,
     buf: &mut Vec<u8>,
-    io_blksize: &Option<usize>,
+    io_blksize: &Option<u64>,
 ) -> std::io::Result<u64>
 where
     R: BufRead,
 {
     // Set read limit to io_blksize if specified
-    // Otherwise to OPT_IO_BLKSIZE_MAX
-    let read_limit = io_blksize.unwrap_or(OPT_IO_BLKSIZE_MAX) as u64;
+    let read_limit: u64 = if let Some(custom_blksize) = io_blksize {
+        *custom_blksize
+    } else {
+        // otherwise try to get it from filesystem, or use default
+        uucore::fs::sane_blksize::sane_blksize_from_path(Path::new(input))
+    };
 
     // Try to read into buffer up to a limit
     let num_bytes = reader
@@ -1635,7 +1620,7 @@ fn split(settings: &Settings) -> UResult<()> {
         Box::new(r) as Box<dyn Read>
     };
     let mut reader = if let Some(c) = settings.io_blksize {
-        BufReader::with_capacity(c, r_box)
+        BufReader::with_capacity(c.try_into().unwrap(), r_box)
     } else {
         BufReader::new(r_box)
     };

src/uucore/src/lib/features/fs.rs

@@ -743,6 +743,55 @@ pub fn path_ends_with_terminator(path: &Path) -> bool {
         .map_or(false, |wide| wide == b'/'.into() || wide == b'\\'.into())
 }
 
+pub mod sane_blksize {
+
+    #[cfg(not(target_os = "windows"))]
+    use std::os::unix::fs::MetadataExt;
+    use std::{fs::metadata, path::Path};
+
+    pub const DEFAULT: u64 = 512;
+    pub const MAX: u64 = (u32::MAX / 8 + 1) as u64;
+
+    /// Provides sanity checked blksize value from the provided value.
+    ///
+    /// If the provided value is a invalid values a meaningful adaption
+    /// of that value is done.
+    pub fn sane_blksize(st_blksize: u64) -> u64 {
+        match st_blksize {
+            0 => DEFAULT,
+            1..=MAX => st_blksize,
+            _ => DEFAULT,
+        }
+    }
+
+    /// Provides the blksize information from the provided metadata.
+    ///
+    /// If the metadata contain invalid values a meaningful adaption
+    /// of that value is done.
+    pub fn sane_blksize_from_metadata(_metadata: &std::fs::Metadata) -> u64 {
+        #[cfg(not(target_os = "windows"))]
+        {
+            sane_blksize(_metadata.blksize())
+        }
+
+        #[cfg(target_os = "windows")]
+        {
+            DEFAULT
+        }
+    }
+
+    /// Provides the blksize information from given file path's filesystem.
+    ///
+    /// If the metadata can't be fetched or contain invalid values a
+    /// meaningful adaption of that value is done.
+    pub fn sane_blksize_from_path(path: &Path) -> u64 {
+        match metadata(path) {
+            Ok(metadata) => sane_blksize_from_metadata(&metadata),
+            Err(_) => DEFAULT,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     // Note this useful idiom: importing names from outer (for mod tests) scope.
@@ -970,4 +1019,13 @@ mod tests {
         assert!(path_ends_with_terminator(Path::new("/")));
         assert!(path_ends_with_terminator(Path::new("C:\\")));
     }
+
+    #[test]
+    fn test_sane_blksize() {
+        assert_eq!(512, sane_blksize::sane_blksize(0));
+        assert_eq!(512, sane_blksize::sane_blksize(512));
+        assert_eq!(4096, sane_blksize::sane_blksize(4096));
+        assert_eq!(0x2000_0000, sane_blksize::sane_blksize(0x2000_0000));
+        assert_eq!(512, sane_blksize::sane_blksize(0x2000_0001));
+    }
 }