Description
In the Linux kernel, the following vulnerability has been resolved:
mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()
mtd_add_partition() does not reject the special offset value
MTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in
add_mtd_device() when called through the BLKPG ioctl on NAND
devices. The RETAIN value depends on cur_offset being the end of
the previous partition, but in the dynamic partition path
cur_offset equals the offset argument itself, causing undefined
behavior.
Commit 5daa7b21496a ("mtd: prepare partition add and del functions
for ioctl requests") introduced mtd_add_partition() and correctly
rejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2),
since those special offsets rely on cur_offset tracking the
previous partition's end. However, commit 1a31368bf92e ("mtd: add a flags
for partitions which should just leave smth. after them")
later added MTDPART_OFS_RETAIN (-3) for the static
partition table path without updating mtd_add_partition() to
also reject this value.
With offset=-3 passed via BLKPG, the RETAIN size calculation in
allocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD
= parent_size + 3). If the underflow result does not appear to
leave enough space, allocate_partition() jumps to out_register via
goto, skipping erasesize initialization. This results in
erasesize=0, which triggers:
WARN_ON((!mtd->erasesize || !master->_erase) &&
!(mtd->flags & MTD_NO_ERASE))
in add_mtd_device(). If the underflow result appears to leave
enough space, a bogus partition size is calculated, but the
"out of reach" sanity check catches the invalid offset and
creates a disabled empty partition (offset=0, size=0) instead
of returning an error.
Fix this by adding MTDPART_OFS_RETAIN to the rejection list in
mtd_add_partition(), consistent with the existing handling of
APPEND and NXTBLK.
mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition()
mtd_add_partition() does not reject the special offset value
MTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in
add_mtd_device() when called through the BLKPG ioctl on NAND
devices. The RETAIN value depends on cur_offset being the end of
the previous partition, but in the dynamic partition path
cur_offset equals the offset argument itself, causing undefined
behavior.
Commit 5daa7b21496a ("mtd: prepare partition add and del functions
for ioctl requests") introduced mtd_add_partition() and correctly
rejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2),
since those special offsets rely on cur_offset tracking the
previous partition's end. However, commit 1a31368bf92e ("mtd: add a flags
for partitions which should just leave smth. after them")
later added MTDPART_OFS_RETAIN (-3) for the static
partition table path without updating mtd_add_partition() to
also reject this value.
With offset=-3 passed via BLKPG, the RETAIN size calculation in
allocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD
= parent_size + 3). If the underflow result does not appear to
leave enough space, allocate_partition() jumps to out_register via
goto, skipping erasesize initialization. This results in
erasesize=0, which triggers:
WARN_ON((!mtd->erasesize || !master->_erase) &&
!(mtd->flags & MTD_NO_ERASE))
in add_mtd_device(). If the underflow result appears to leave
enough space, a bogus partition size is calculated, but the
"out of reach" sanity check catches the invalid offset and
creates a disabled empty partition (offset=0, size=0) instead
of returning an error.
Fix this by adding MTDPART_OFS_RETAIN to the rejection list in
mtd_add_partition(), consistent with the existing handling of
APPEND and NXTBLK.
Published:
2026-09-17
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
|
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No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition() mtd_add_partition() does not reject the special offset value MTDPART_OFS_RETAIN (-3), which leads to a WARN_ON in add_mtd_device() when called through the BLKPG ioctl on NAND devices. The RETAIN value depends on cur_offset being the end of the previous partition, but in the dynamic partition path cur_offset equals the offset argument itself, causing undefined behavior. Commit 5daa7b21496a ("mtd: prepare partition add and del functions for ioctl requests") introduced mtd_add_partition() and correctly rejected MTDPART_OFS_APPEND (-1) and MTDPART_OFS_NXTBLK (-2), since those special offsets rely on cur_offset tracking the previous partition's end. However, commit 1a31368bf92e ("mtd: add a flags for partitions which should just leave smth. after them") later added MTDPART_OFS_RETAIN (-3) for the static partition table path without updating mtd_add_partition() to also reject this value. With offset=-3 passed via BLKPG, the RETAIN size calculation in allocate_partition() underflows (parent_size - 0xFFFFFFFFFFFFFFFD = parent_size + 3). If the underflow result does not appear to leave enough space, allocate_partition() jumps to out_register via goto, skipping erasesize initialization. This results in erasesize=0, which triggers: WARN_ON((!mtd->erasesize || !master->_erase) && !(mtd->flags & MTD_NO_ERASE)) in add_mtd_device(). If the underflow result appears to leave enough space, a bogus partition size is calculated, but the "out of reach" sanity check catches the invalid offset and creates a disabled empty partition (offset=0, size=0) instead of returning an error. Fix this by adding MTDPART_OFS_RETAIN to the rejection list in mtd_add_partition(), consistent with the existing handling of APPEND and NXTBLK. | |
| Title | mtd: part: reject MTDPART_OFS_RETAIN in mtd_add_partition() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:10:39.008Z
Reserved: 2026-09-17T15:57:05.658Z
Link: CVE-2026-93048
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:58.080
Modified: 2026-09-17T17:17:58.080
Link: CVE-2026-93048
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.