[PATCH proxmox-backup 6/9] datastore: check that index files are regular files

[Robert Obkircher <r.obkircher@proxmox.com>]

Return an explicit error message when trying to mmap something other
than a regular file. Previously, this was caught implicitly by the
non-zero size check or by a failing seek.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 pbs-datastore/src/dynamic_index.rs | 16 ++++++++--------
 pbs-datastore/src/fixed_index.rs   | 15 ++++++++-------
 2 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/pbs-datastore/src/dynamic_index.rs b/pbs-datastore/src/dynamic_index.rs
index 7ee8bdcab..dd0b86f3f 100644
--- a/pbs-datastore/src/dynamic_index.rs
+++ b/pbs-datastore/src/dynamic_index.rs
@@ -8,6 +8,7 @@ use std::sync::{Arc, Mutex};
 use std::task::Context;
 
 use anyhow::{Error, bail, format_err};
+use nix::sys::stat::{SFlag, fstat};
 
 use proxmox_io::ReadExt;
 use proxmox_sys::mmap::Mmap;
@@ -96,17 +97,16 @@ impl DynamicIndexReader {
     }
 
     pub fn new(mut file: std::fs::File) -> Result<Self, Error> {
+        let stat = fstat(file.as_raw_fd()).map_err(|e| format_err!("fstat failed - {e}"))?;
+        if (stat.st_mode & SFlag::S_IFMT.bits()) != SFlag::S_IFREG.bits() {
+            bail!("not a regular file");
+        }
+
         // FIXME: This is NOT OUR job! Check the callers of this method and remove this!
         file.seek(SeekFrom::Start(0))?;
 
         let header_size = std::mem::size_of::<DynamicIndexHeader>();
 
-        let rawfd = file.as_raw_fd();
-        let stat = match nix::sys::stat::fstat(rawfd) {
-            Ok(stat) => stat,
-            Err(err) => bail!("fstat failed - {}", err),
-        };
-
         let size = stat.st_size as usize;
 
         if size < header_size {
@@ -611,11 +611,11 @@ mod tests {
 
         check_error_contains(
             DynamicIndexReader::open(Path::new("/dev/stdin")),
-            "Illegal seek",
+            "not a regular file",
         );
         check_error_contains(
             DynamicIndexReader::open(Path::new("/dev/zero")),
-            "index too small (0)",
+            "not a regular file",
         );
 
         let path = dir.path().join("file");
diff --git a/pbs-datastore/src/fixed_index.rs b/pbs-datastore/src/fixed_index.rs
index 0145f93d3..1d3d0170a 100644
--- a/pbs-datastore/src/fixed_index.rs
+++ b/pbs-datastore/src/fixed_index.rs
@@ -5,6 +5,7 @@ use std::path::{Path, PathBuf};
 use std::ptr::NonNull;
 
 use anyhow::{Context, Error, bail, format_err};
+use nix::sys::stat::{SFlag, fstat};
 
 use proxmox_io::ReadExt;
 use proxmox_uuid::Uuid;
@@ -60,15 +61,15 @@ impl FixedIndexReader {
     }
 
     pub fn new(mut file: std::fs::File) -> Result<Self, Error> {
+        let stat = fstat(file.as_raw_fd()).map_err(|e| format_err!("fstat failed - {e}"))?;
+        if (stat.st_mode & SFlag::S_IFMT.bits()) != SFlag::S_IFREG.bits() {
+            bail!("not a regular file");
+        }
+
         file.seek(SeekFrom::Start(0))?;
 
         let header_size = std::mem::size_of::<FixedIndexHeader>();
 
-        let stat = match nix::sys::stat::fstat(file.as_raw_fd()) {
-            Ok(stat) => stat,
-            Err(err) => bail!("fstat failed - {}", err),
-        };
-
         let size = stat.st_size as usize;
 
         if size < header_size {
@@ -608,11 +609,11 @@ mod tests {
 
         check_error_contains(
             FixedIndexReader::open(Path::new("/dev/stdin")),
-            "Illegal seek",
+            "not a regular file",
         );
         check_error_contains(
             FixedIndexReader::open(Path::new("/dev/zero")),
-            "index too small (0)",
+            "not a regular file",
         );
 
         let path = dir.path().join("file");
-- 
2.47.3