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fs: nvs: prevent ATE writes at sector boundary

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In NVS, allocation table entries (ATEs) are written backwards within
each sector. Under delete-only or delete-heavy workloads, a sector may
contain only delete ATEs, causing the ATE write pointer to approach the
sector boundary.

Without an explicit boundary check, ATE writes may occur at offset 0 of
the current sector, allowing the write pointer to underflow into the
previous sector and corrupt unrelated data or metadata.

Fix this by disallowing ATE writes when the write pointer is at the
sector boundary. This ensures that ATE writes remain confined to the
current sector and prevents pointer underflow across sectors.

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>
This commit is contained in:
Lingao Meng
2026-01-20 16:44:12 +08:00
committed by Fabio Baltieri
parent 73c182509c
commit d845a2230e
1 changed files with 7 additions and 1 deletions
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8
subsys/fs/nvs/nvs.c
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@@ -1176,7 +1176,13 @@ no_cached_entry:
goto end;
}
if (fs->ate_wra >= (fs->data_wra + required_space)) {
/* ATEs grow backwards within a sector. In delete-only scenarios,
* a sector may contain only delete ATEs and no data entries.
* Prevent ATE writes at current start of sector to avoid crossing
* into the previous sector.
*/
if (fs->ate_wra >= (fs->data_wra + required_space) &&
(fs->ate_wra & ADDR_OFFS_MASK) != 0) {
rc = nvs_flash_wrt_entry(fs, id, data, len);
if (rc) {