df: better error message when executed in a chroot without /proc #3601

src/uu/df/src/df.rs

@@ -14,7 +14,7 @@ mod table;
 use blocks::HumanReadable;
 use table::HeaderMode;
 use uucore::display::Quotable;
-use uucore::error::{UError, UResult, USimpleError};
+use uucore::error::{UError, UIoError, UResult, USimpleError};
 use uucore::fsext::{read_fs_list, MountInfo};
 use uucore::parse_size::ParseSizeError;
 use uucore::{format_usage, show};
@@ -333,7 +333,7 @@ fn filter_mount_list(vmi: Vec<MountInfo>, opt: &Options) -> Vec<MountInfo> {
 /// `opt` excludes certain filesystems from consideration and allows for the synchronization of filesystems before running; see
 /// [`Options`] for more information.
 
-fn get_all_filesystems(opt: &Options) -> Vec<Filesystem> {
+fn get_all_filesystems(opt: &Options) -> Result<Vec<Filesystem>, std::io::Error> {
     // Run a sync call before any operation if so instructed.
     if opt.sync {
         #[cfg(not(windows))]
@@ -349,19 +349,19 @@ fn get_all_filesystems(opt: &Options) -> Vec<Filesystem> {
     //
     // Filesystems excluded by the command-line options are
     // not considered.
-    let mounts: Vec<MountInfo> = filter_mount_list(read_fs_list(), opt);
+    let mounts: Vec<MountInfo> = filter_mount_list(read_fs_list()?, opt);
 
     // Convert each `MountInfo` into a `Filesystem`, which contains
     // both the mount information and usage information.
-    mounts
+    Ok(mounts
         .into_iter()
         .filter_map(|m| Filesystem::new(m, None))
         .filter(|fs| opt.show_all_fs || fs.usage.blocks > 0)
-        .collect()
+        .collect())
 }
 
 /// For each path, get the filesystem that contains that path.
-fn get_named_filesystems<P>(paths: &[P], opt: &Options) -> Vec<Filesystem>
+fn get_named_filesystems<P>(paths: &[P], opt: &Options) -> Result<Vec<Filesystem>, std::io::Error>
 where
     P: AsRef<Path>,
 {
@@ -371,7 +371,7 @@ where
     // considered. The "lofs" filesystem is a loopback
     // filesystem present on Solaris and FreeBSD systems. It
     // is similar to a symbolic link.
-    let mounts: Vec<MountInfo> = filter_mount_list(read_fs_list(), opt)
+    let mounts: Vec<MountInfo> = filter_mount_list(read_fs_list()?, opt)
         .into_iter()
         .filter(|mi| mi.fs_type != "lofs" && !mi.dummy)
         .collect();
@@ -381,7 +381,7 @@ where
     // this happens if the file system type doesn't exist
     if mounts.is_empty() {
         show!(USimpleError::new(1, "no file systems processed"));
-        return result;
+        return Ok(result);
     }
 
     // Convert each path into a `Filesystem`, which contains
@@ -402,7 +402,7 @@ where
             }
         }
     }
-    result
+    Ok(result)
 }
 
 #[derive(Debug)]
@@ -443,7 +443,15 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     // Get the list of filesystems to display in the output table.
     let filesystems: Vec<Filesystem> = match matches.values_of(OPT_PATHS) {
         None => {
-            let filesystems = get_all_filesystems(&opt);
+            let filesystems = match get_all_filesystems(&opt) {
+                Ok(filesystems) => filesystems,
+                Err(error) => {
+                    return Err(UIoError::new(
+                        error.kind(),
+                        format!("cannot read table of mounted file systems"),
+                    ));
+                }
+            };
 
             if filesystems.is_empty() {
                 return Err(USimpleError::new(1, "no file systems processed"));
@@ -453,7 +461,15 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         }
         Some(paths) => {
             let paths: Vec<&str> = paths.collect();
-            let filesystems = get_named_filesystems(&paths, &opt);
+            let filesystems = match get_named_filesystems(&paths, &opt) {
+                Ok(filesystems) => filesystems,
+                Err(error) => {
+                    return Err(UIoError::new(
+                        error.kind(),
+                        format!("cannot read table of mounted file systems"),
+                    ));
+                }
+            };
 
             // This can happen if paths are given as command-line arguments
             // but none of the paths exist.

src/uu/stat/src/stat.rs

@@ -501,7 +501,7 @@ impl Stater {
             // mount points aren't displayed when showing filesystem information
             None
         } else {
-            let mut mount_list = read_fs_list()
+            let mut mount_list = read_fs_list()?
                 .iter()
                 .map(|mi| mi.mount_dir.clone())
                 .collect::<Vec<String>>();

src/uucore/src/lib/features/fsext.rs

@@ -405,22 +405,21 @@ use std::ptr;
 ))]
 use std::slice;
 /// Read file system list.
-pub fn read_fs_list() -> Vec<MountInfo> {
+pub fn read_fs_list() -> Result<Vec<MountInfo>, std::io::Error> {
     #[cfg(any(target_os = "linux", target_os = "android"))]
     {
         let (file_name, f) = File::open(LINUX_MOUNTINFO)
             .map(|f| (LINUX_MOUNTINFO, f))
-            .or_else(|_| File::open(LINUX_MTAB).map(|f| (LINUX_MTAB, f)))
-            .expect("failed to find mount list files");
+            .or_else(|_| File::open(LINUX_MTAB).map(|f| (LINUX_MTAB, f)))?;
         let reader = BufReader::new(f);
-        reader
+        Ok(reader
             .lines()
             .filter_map(|line| line.ok())
             .filter_map(|line| {
                 let raw_data = line.split_whitespace().collect::<Vec<&str>>();
                 MountInfo::new(file_name, &raw_data)
             })
-            .collect::<Vec<_>>()
+            .collect::<Vec<_>>())
     }
     #[cfg(any(
         target_os = "freebsd",
@@ -435,10 +434,10 @@ pub fn read_fs_list() -> Vec<MountInfo> {
             crash!(1, "get_mount_info() failed");
         }
         let mounts = unsafe { slice::from_raw_parts(mount_buffer_ptr, len as usize) };
-        mounts
+        Ok(mounts
             .iter()
             .map(|m| MountInfo::from(*m))
-            .collect::<Vec<_>>()
+            .collect::<Vec<_>>())
     }
     #[cfg(windows)]
     {
@@ -482,12 +481,12 @@ pub fn read_fs_list() -> Vec<MountInfo> {
         unsafe {
             FindVolumeClose(find_handle);
         }
-        mounts
+        Ok(mounts)
     }
     #[cfg(any(target_os = "redox", target_os = "illumos", target_os = "solaris"))]
     {
         // No method to read mounts, yet
-        Vec::new()
+        Ok(Vec::new())
     }
 }