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Message-ID: <20251120154400.1042123-1-yun.zhou@windriver.com>
Date: Thu, 20 Nov 2025 23:44:00 +0800
From: Yun Zhou <yun.zhou@...driver.com>
To: <shaggy@...nel.org>
CC: <rand.sec96@...il.com>, <contact@...aud-lcm.com>, <kovalev@...linux.org>,
<zheng.yu@...thwestern.edu>, <eadavis@...com>,
<yun.zhou@...driver.com>, <jfs-discussion@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>
Subject: [PATCH] jfs: add dtpage integrity check to prevent index/pointer overflows
Add check_dtpage() to validate dtpage_t integrity, focusing on
preventing index/pointer overflows from on-disk corruption.
Key checks:
- maxslot must be exactly DTPAGEMAXSLOT (128) as defined for dtpage
slot array.
- freecnt bounded by [0, DTPAGEMAXSLOT-1] (slot[0] reserved for header).
- freelist validity: -1 when freecnt=0; 1~DTPAGEMAXSLOT-1 when non-zero,
with linked list checks (no duplicates, proper termination via next=-1).
- stblindex bounds: must be within range that avoids overlapping with
stbl itself (stblindex < DTPAGEMAXSLOT - stblsize).
- nextindex bounded by stbl size (stblsize << L2DTSLOTSIZE). stbl entries
validity: within 1~DTPAGEMAXSLOT-1, no duplicates(excluding invalid
entries marked as -1).
Invoked when loading dtpage (in BT_GETPAGE macro context) to catch
corruption early before directory operations trigger out-of-bounds access.
Signed-off-by: Yun Zhou <yun.zhou@...driver.com>
---
fs/jfs/jfs_dtree.c | 108 +++++++++++++++++++++++++++++++++++++++++++--
fs/jfs/jfs_dtree.h | 2 +
2 files changed, 106 insertions(+), 4 deletions(-)
diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index e1cbc3a04f3f..6df4a3ed9043 100644
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -115,10 +115,7 @@ struct dtsplit {
do { \
BT_GETPAGE(IP, BN, MP, dtpage_t, SIZE, P, RC, i_dtroot); \
if (!(RC)) { \
- if (((P)->header.nextindex > \
- (((BN) == 0) ? DTROOTMAXSLOT : (P)->header.maxslot)) || \
- ((BN) && (((P)->header.maxslot > DTPAGEMAXSLOT) || \
- ((P)->header.stblindex >= DTPAGEMAXSLOT)))) { \
+ if ((BN) && !check_dtpage(P)) { \
BT_PUTPAGE(MP); \
jfs_error((IP)->i_sb, \
"DT_GETPAGE: dtree page corrupt\n"); \
@@ -4399,3 +4396,106 @@ bool check_dtroot(dtroot_t *p)
return true;
}
+
+bool check_dtpage(dtpage_t *p)
+{
+ DECLARE_BITMAP(bitmap, DTPAGEMAXSLOT) = {0};
+ const int stblsize = ((PSIZE >> L2DTSLOTSIZE) + 31) >> L2DTSLOTSIZE;
+ int i;
+
+ /* Validate maxslot (maximum number of slots in the page)
+ * dtpage_t slot array is defined to hold up to DTPAGEMAXSLOT (128) slots
+ */
+ if (unlikely(p->header.maxslot != DTPAGEMAXSLOT)) {
+ jfs_err("Bad maxslot:%d in dtpage (expected %d)\n",
+ p->header.maxslot, DTPAGEMAXSLOT);
+ return false;
+ }
+
+ /* freecnt cannot be negative or exceed DTPAGEMAXSLOT-1
+ * (since slot[0] is occupied by the header).
+ */
+ if (unlikely(p->header.freecnt < 0 ||
+ p->header.freecnt > DTPAGEMAXSLOT - 1)) {
+ jfs_err("Bad freecnt:%d in dtpage\n", p->header.freecnt);
+ return false;
+ } else if (p->header.freecnt == 0) {
+ /* No free slots: freelist must be -1 */
+ if (unlikely(p->header.freelist != -1)) {
+ jfs_err("freecnt=0 but freelist=%d in dtpage\n",
+ p->header.freelist);
+ return false;
+ }
+ } else {
+ int fsi;
+ /* When there are free slots, freelist must be a valid slot index in
+ * 1~DTROOTMAXSLOT-1(since slot[0] is occupied by the header).
+ */
+ if (unlikely(p->header.freelist < 1 ||
+ p->header.freelist >= DTPAGEMAXSLOT)) {
+ jfs_err("Bad freelist:%d in dtpage\n", p->header.freelist);
+ return false;
+ }
+
+ /* Traverse the free list to check validity of all node indices */
+ fsi = p->header.freelist;
+ for (i = 0; i < p->header.freecnt - 1; i++) {
+ /* Check for duplicate indices in the free list */
+ if (unlikely(__test_and_set_bit(fsi, bitmap))) {
+ jfs_err("duplicate index%d in slot in dtpage\n", fsi);
+ return false;
+ }
+ fsi = p->slot[fsi].next;
+
+ /* Ensure the next slot index in the free list is valid */
+ if (unlikely(fsi < 1 || fsi >= DTPAGEMAXSLOT)) {
+ jfs_err("Bad index:%d in slot in dtpage\n", fsi);
+ return false;
+ }
+ }
+
+ /* The last node in the free list must terminate with next = -1 */
+ if (unlikely(p->slot[fsi].next != -1)) {
+ jfs_err("Bad next:%d of the last slot in dtpage\n",
+ p->slot[fsi].next);
+ return false;
+ }
+ }
+
+ /* stbl must be little then DTPAGEMAXSLOT */
+ if (unlikely(p->header.stblindex >= DTPAGEMAXSLOT - stblsize)) {
+ jfs_err("Bad stblindex:%d in dtpage (stbl size %d)\n",
+ p->header.stblindex, stblsize);
+ return false;
+ }
+
+ /* nextindex must be little then stblsize*32 */
+ if (unlikely(p->header.nextindex >= (stblsize << L2DTSLOTSIZE))) {
+ jfs_err("Bad nextindex:%d in dtpage (stbl size %d)\n",
+ p->header.nextindex, stblsize);
+ return false;
+ }
+
+ /* Validate stbl entries
+ * Each entry is a slot index, valid range: -1 (invalid) or [0, nextindex-1] (valid data slots)
+ * (stblindex and higher slots are reserved for stbl itself)
+ */
+ for (i = 0; i < p->header.nextindex; i++) {
+ int idx = DT_GETSTBL(p)[i];
+
+ /* Check if index is out of valid data slot range */
+ if (unlikely(idx < 1 || idx >= DTPAGEMAXSLOT)) {
+ jfs_err("Bad stbl[%d] index:%d (stblindex %d) in dtpage\n",
+ i, idx, p->header.stblindex);
+ return false;
+ }
+
+ /* Check for duplicate valid indices (skip -1) */
+ if (unlikely(__test_and_set_bit(idx, bitmap))) {
+ jfs_err("Duplicate index:%d in stbl of dtpage\n", idx);
+ return false;
+ }
+ }
+
+ return true;
+}
diff --git a/fs/jfs/jfs_dtree.h b/fs/jfs/jfs_dtree.h
index 94dc16123c87..dfc87b6690a9 100644
--- a/fs/jfs/jfs_dtree.h
+++ b/fs/jfs/jfs_dtree.h
@@ -255,4 +255,6 @@ extern int dtModify(tid_t tid, struct inode *ip, struct component_name * key,
extern int jfs_readdir(struct file *file, struct dir_context *ctx);
extern bool check_dtroot(dtroot_t *p);
+
+extern bool check_dtpage(dtpage_t *p);
#endif /* !_H_JFS_DTREE */
--
2.34.1
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