[pbs-devel] [PATCH proxmox-backup v4] fix #4380: check if file is excluded before running `stat()`

[Gabriel Goller]

Passed a closure with the `stat()` function call to `match_mode_lazy()`. This
will traverse through all patterns and try to match using the path only, if a
`file_mode` is needed, it will run the closure. This means that if we exclude
a file with the `MatchType::ANY_FILE_TYPE`, we will skip it without running
`stat()` on it.
Added `pathpatterns` crate to local overrides in cargo.toml.

Signed-off-by: Gabriel Goller <g.goller at proxmox.com>
---

changes v3:
 - match only by path and exclude the matched files, the run `stat()` and
   match again, this time using the `file_mode`. This will match everything 
   twice in the worst case, which is not optimal.
changes v2:
 - checking for `read` and `execute` permissions before entering directory,
   doesn't work because there are a lot of side-effects (executed by
   different user, AppArmor, SELinux, ...).
changes v1:
 - checking for excluded files with `matches()` before executing `stat()`,
   this doesn't work because we get the file_mode from `stat()` and don't
   want to ignore it when matching.

 Cargo.toml                    |  1 +
 pbs-client/src/pxar/create.rs | 68 +++++++++++++++++++++++++----------
 2 files changed, 50 insertions(+), 19 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 2a05c471..c54bc28b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -262,6 +262,7 @@ proxmox-rrd.workspace = true
 
 #proxmox-apt = { path = "../proxmox-apt" }
 #proxmox-openid = { path = "../proxmox-openid-rs" }
+#pathpatterns = {path = "../pathpatterns" }
 
 #pxar = { path = "../pxar" }
 
diff --git a/pbs-client/src/pxar/create.rs b/pbs-client/src/pxar/create.rs
index 2577cf98..7027a7d2 100644
--- a/pbs-client/src/pxar/create.rs
+++ b/pbs-client/src/pxar/create.rs
@@ -21,7 +21,6 @@ use pxar::Metadata;
 
 use proxmox_io::vec;
 use proxmox_lang::c_str;
-use proxmox_sys::error::SysError;
 use proxmox_sys::fs::{self, acl, xattr};
 
 use pbs_datastore::catalog::BackupCatalogWriter;
@@ -420,7 +419,7 @@ impl Archiver {
         for file in dir.iter() {
             let file = file?;
 
-            let file_name = file.file_name().to_owned();
+            let file_name = file.file_name();
             let file_name_bytes = file_name.to_bytes();
             if file_name_bytes == b"." || file_name_bytes == b".." {
                 continue;
@@ -434,25 +433,56 @@ impl Archiver {
             assert_single_path_component(os_file_name)?;
             let full_path = self.path.join(os_file_name);
 
-            let stat = match nix::sys::stat::fstatat(
-                dir_fd,
-                file_name.as_c_str(),
-                nix::fcntl::AtFlags::AT_SYMLINK_NOFOLLOW,
-            ) {
-                Ok(stat) => stat,
-                Err(ref err) if err.not_found() => continue,
-                Err(err) => return Err(err).context(format!("stat failed on {:?}", full_path)),
-            };
-
             let match_path = PathBuf::from("/").join(full_path.clone());
-            if self
-                .patterns
-                .matches(match_path.as_os_str().as_bytes(), Some(stat.st_mode))
-                == Some(MatchType::Exclude)
-            {
+
+            let mut stat_results: Option<FileStat> = None;
+
+            let stat =
+                self.patterns
+                    .matches_mode_lazy(match_path.as_os_str().as_bytes(), || {
+                        match nix::sys::stat::fstatat(
+                            dir_fd,
+                            file_name.to_owned().as_c_str(),
+                            nix::fcntl::AtFlags::AT_SYMLINK_NOFOLLOW,
+                        ) {
+                            Ok(stat) => {
+                                stat_results = Some(stat);
+                                Ok(stat.st_mode)
+                            }
+                            Err(e) => Err(e),
+                        }
+                    })
+                    .map_err(|err| {
+                        anyhow::Error::new(err).context(format!(
+                            "stat failed on {:?} with {:?}",
+                            full_path,
+                            err.desc()
+                        ))
+                    })?;
+
+            if stat == Some(MatchType::Exclude) {
                 continue;
             }
 
+            if stat_results.is_none() {
+                match nix::sys::stat::fstatat(
+                    dir_fd,
+                    file_name.to_owned().as_c_str(),
+                    nix::fcntl::AtFlags::AT_SYMLINK_NOFOLLOW,
+                ) {
+                    Ok(stat) => {
+                        stat_results = Some(stat);
+                    }
+                    Err(err) => {
+                        return Err(err).context(format!(
+                            "stat failed on {:?} with {:?}",
+                            full_path,
+                            err.desc()
+                        ));
+                    }
+                }
+            }
+
             self.entry_counter += 1;
             if self.entry_counter > self.entry_limit {
                 bail!(
@@ -462,9 +492,9 @@ impl Archiver {
             }
 
             file_list.push(FileListEntry {
-                name: file_name,
+                name: file_name.to_owned(),
                 path: full_path,
-                stat,
+                stat: stat_results.unwrap(),
             });
         }
 
-- 
2.39.2