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Merge: CVE-2026-23002: lib/buildid: use __kernel_read() for sleepable context

Browse Source 
MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/8297

JIRA: https://redhat.atlassian.net/browse/RHEL-189963
CVE: CVE-2026-23002

Backported from tree(s): linux

```
lib/buildid: use __kernel_read() for sleepable context

Prevent a "BUG: unable to handle kernel NULL pointer dereference in
filemap_read_folio".

For the sleepable context, convert freader to use __kernel_read() instead
of direct page cache access via read_cache_folio().  This simplifies the
faultable code path by using the standard kernel file reading interface
which handles all the complexity of reading file data.

At the moment we are not changing the code for non-sleepable context which
uses filemap_get_folio() and only succeeds if the target folios are
already in memory and up-to-date.  The reason is to keep the patch simple
and easier to backport to stable kernels.

Syzbot repro does not crash the kernel anymore and the selftests run
successfully.

In the follow up we will make __kernel_read() with IOCB_NOWAIT work for
non-sleepable contexts.  In addition, I would like to replace the
secretmem check with a more generic approach and will add fstest for the
buildid code.

Link: https://lkml.kernel.org/r/20251222205859.3968077-1-shakeel.butt@linux.dev
Fixes: ad41251c290d ("lib/buildid: implement sleepable build_id_parse() API")
Reported-by: syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jinchao Wang <wangjinchao600@gmail.com>
  Link: https://lkml.kernel.org/r/aUteBPWPYzVWIZFH@ndev
Reviewed-by: Christian Brauner <brauner@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Daniel Borkman <daniel@iogearbox.net>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 777a8560fd29738350c5094d4166fe5499452409)

```

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>
[^footer]: Created 2026-06-29 12:51 UTC by backporter - [KWF FAQ](https://red.ht/kernel_workflow_doc) - [Slack #team-kernel-workflow](https://redhat-internal.slack.com/archives/C04LRUPMJQ5) - [Source](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/webhook/utils/backporter.py) - [Documentation](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/docs/README.backporter.md) - [Report an issue](https://redhat.atlassian.net/secure/CreateIssueDetails!init.jspa?pid=11779&issuetype=10016&priority=10001&summary=backporter+webhook+issue&components=66291) [^footer]

Approved-by: Ines Qian <iqian@redhat.com>
Approved-by: Rafael Aquini <raquini@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>
This commit is contained in:
CKI KWF Bot
2026-07-27 08:12:02 +00:00
parent 9e3b5c1cad 401e5da13e
commit 876bb99dff
1 changed files with 20 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/buildid.c
+20 -12
View File
@@ -5,6 +5,7 @@
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/pagemap.h>
#include <linux/fs.h>
#include <linux/secretmem.h>
#define BUILD_ID 3
@@ -65,20 +66,9 @@ static int freader_get_folio(struct freader *r, loff_t file_off)
freader_put_folio(r);
/* reject secretmem folios created with memfd_secret() */
if (secretmem_mapping(r->file->f_mapping))
return -EFAULT;
/* only use page cache lookup - fail if not already cached */
r->folio = filemap_get_folio(r->file->f_mapping, file_off >> PAGE_SHIFT);
/* if sleeping is allowed, wait for the page, if necessary */
if (r->may_fault && (IS_ERR(r->folio) || !folio_test_uptodate(r->folio))) {
filemap_invalidate_lock_shared(r->file->f_mapping);
r->folio = read_cache_folio(r->file->f_mapping, file_off >> PAGE_SHIFT,
NULL, r->file);
filemap_invalidate_unlock_shared(r->file->f_mapping);
}
if (IS_ERR(r->folio) || !folio_test_uptodate(r->folio)) {
if (!IS_ERR(r->folio))
folio_put(r->folio);
@@ -116,6 +106,24 @@ static const void *freader_fetch(struct freader *r, loff_t file_off, size_t sz)
return r->data + file_off;
}
/* reject secretmem folios created with memfd_secret() */
if (secretmem_mapping(r->file->f_mapping)) {
r->err = -EFAULT;
return NULL;
}
/* use __kernel_read() for sleepable context */
if (r->may_fault) {
ssize_t ret;
ret = __kernel_read(r->file, r->buf, sz, &file_off);
if (ret != sz) {
r->err = (ret < 0) ? ret : -EIO;
return NULL;
}
return r->buf;
}
/* fetch or reuse folio for given file offset */
r->err = freader_get_folio(r, file_off);
if (r->err)