[Rpm-maint] [rpm-software-management/rpm] fix: chdir after chroot so cwd is valid inside --root transactions (PR #4305)
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Tue Aug 11 13:36:59 UTC 2026
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**Actionable comments posted: 2**
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Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@lib/rpmchroot.c`:
- Line 152: Update rpmChrootIn so rootState.chrootDone is set immediately after
chroot() succeeds, before attempting chdir("/"). If chdir("/") fails, preserve
errno, call rpmChrootOut() immediately to restore the original root and working
directory, then use the preserved errno for error reporting.
- Around line 113-117: Update rpmChrootSet() so a failed open("/") does not
retain partial rootState configuration: clear rootState.rootDir (and any
associated state) when rootState.root_fd is invalid, or require both
rootState.cwd and rootState.root_fd to be valid before taking the same-root
no-op path. Ensure a later call retries opening the root and cannot enter with
an invalid descriptor.
```
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<summary>🪄 Autofix</summary>
Fix all unresolved CodeRabbit comments on this PR:
- [ ] <!-- {"checkboxId": "4b0d0e0a-96d7-4f10-b296-3a18ea78f0b9"} --> Push a commit to this branch (recommended)
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Reviewing files that changed from the base of the PR and between 9fc611e38004b1ddaa6668297408649ed556c157 and a4ee5f4a6f36adfe0221abe95f999ed62765ef55.
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* `lib/rpmchroot.c`
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> + rootState.root_fd = open("/", O_RDONLY);
+ if (rootState.root_fd < 0) {
+ rpmlog(RPMLOG_ERR, _("Unable to open root directory: %m\n"));
+ rc = -1;
+ }
_🩺 Stability & Availability_ | _🟠 Major_ | _⚡ Quick win_
**Do not retain a failed root configuration.**
If `open("/")` fails, `rpmChrootSet()` returns `-1` but retains `rootState.rootDir`. A later call with the same root returns success at line 87 without reopening `root_fd`. Entry can then succeed, but exit calls `fchdir(-1)` and cannot restore the original root.
Clear the partial state on failure. Alternatively, make the same-root no-op conditional on both `rootState.cwd` and `rootState.root_fd` being valid.
<details>
<summary>Proposed fix</summary>
```diff
- if (rootDir && rootState.rootDir && rstreq(rootDir, rootState.rootDir))
+ if (rootDir && rootState.rootDir && rstreq(rootDir, rootState.rootDir) &&
+ rootState.cwd >= 0 && rootState.root_fd >= 0)
return 0;
```
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<details>
<summary>🤖 Prompt for AI Agents</summary>
```
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@lib/rpmchroot.c` around lines 113 - 117, Update rpmChrootSet() so a failed
open("/") does not retain partial rootState configuration: clear
rootState.rootDir (and any associated state) when rootState.root_fd is invalid,
or require both rootState.cwd and rootState.root_fd to be valid before taking
the same-root no-op path. Ensure a later call retries opening the root and
cannot enter with an invalid descriptor.
```
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> @@ -131,7 +144,12 @@ int rpmChrootIn(void)
try_become_root();
rpmlog(RPMLOG_DEBUG, "entering chroot %s\n", rootState.rootDir);
- if (chdir("/") == 0 && chroot(rootState.rootDir) == 0) {
+ /* chdir("/") must come AFTER chroot(): doing it before leaves the
+ * cwd pointing at the old root's inode, which is not reachable
+ * from inside the new root — every relative path resolution
+ * (realpath/getcwd, e.g. fprint.c canonDir) then fails and rpm
+ * crashes (SIGSEGV 0xF069) during --root transactions. */
+ if (chroot(rootState.rootDir) == 0 && chdir("/") == 0) {
_🩺 Stability & Availability_ | _🔴 Critical_ | _⚡ Quick win_
**Restore the process root if `chdir("/")` fails.**
If `chroot(rootState.rootDir)` succeeds and `chdir("/")` fails, `rootState.chrootDone` remains zero. `rpmPackageInstall()` then does not call `rpmChrootOut()` because `rpmChrootIn()` returned an error. The process remains chrooted while the state reports that it is not.
Set `rootState.chrootDone` after a successful `chroot()`. If `chdir("/")` fails, immediately call `rpmChrootOut()` to restore the original root and working directory. Preserve `errno` before cleanup for the error log.
<details>
<summary>🤖 Prompt for AI Agents</summary>
```
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@lib/rpmchroot.c` at line 152, Update rpmChrootIn so rootState.chrootDone is
set immediately after chroot() succeeds, before attempting chdir("/"). If
chdir("/") fails, preserve errno, call rpmChrootOut() immediately to restore the
original root and working directory, then use the preserved errno for error
reporting.
```
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