GHSA-F98W-WX7Q-XJVQ
Vulnerability from github – Published: 2026-10-23 12:31 – Updated: 2026-10-23 12:31In the Linux kernel, the following vulnerability has been resolved:
mmc: core: Add validation for host-provided max_segs
The max_segs field is of type unsigned short, and if a host driver sets an excessively large value, it may be truncated to zero. This can cause mmc_alloc_sg() to call kmalloc_objs() with a zero size allocation request, which leads to undefined behavior.
Under the SLUB allocator, kmalloc(0) returns a special pointer (ZERO_SIZE_PTR). The subsequent 'if (sg)' check will evaluate to true, and sg_init_table() will then attempt to access invalid memory, resulting in a crash:
dwmmc_rockchip 2a310000.mmc: Successfully tuned phase to 133 mmc1: new UHS-I speed SDR104 SDHC card at address aaaa Unable to handle kernel paging request at virtual address 0000001ffffffff0 Mem abort info: ESR = 0x0000000096000004 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault Data abort info: ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=0000000102c88000 [0000001ffffffff0] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 0000000096000004 [#1] SMP Modules linked in: CPU: 2 UID: 0 PID: 102 Comm: kworker/2:1 Not tainted 7.0.0-rc6-next-20260331-00013-g4d93c25963c5-dirty #80 PREEMPT Hardware name: Rockchip RK3576 EVB V10 Board (DT) Workqueue: events_freezable mmc_rescan pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : sg_init_table+0x2c/0x50 lr : sg_init_table+0x24/0x50 sp : ffff8000837db710 x29: ffff8000837db710 x28: 000000000000c000 x27: 0000000000000300 x26: 0000000000000000 x25: 0000000000000040 x24: ffff0000c46a0000 x23: 0000000000000000 x22: ffff0000c0c73c00 x21: 0000000000000010 x20: 0000000000000010 x19: 0000000000000000 x18: 000000000000002c x17: 0000000000000000 x16: 0000000000000001 x15: 0000000000000000 x14: 0000000000000400 x13: ffff8000837dc000 x12: 0000000000000000 x11: ffff0000c0c73ca0 x10: 0000000000000040 x9 : 459ec1f0abbdbb00 x8 : 0000001fffffffe0 x7 : 0000000000000000 x6 : 000000000000003f x5 : 0000000000035579 x4 : 0000000000000901 x3 : 0000000000000000 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000010 Call trace: sg_init_table+0x2c/0x50 (P) mmc_mq_init_request+0x64/0x90 blk_mq_alloc_map_and_rqs+0x3ac/0x480 blk_mq_alloc_set_map_and_rqs+0x98/0x1e0 blk_mq_alloc_tag_set+0x1c0/0x290 mmc_init_queue+0x120/0x370 mmc_blk_alloc_req+0x150/0x420
To prevent this, add a validation check in mmc_mq_init_request() to detect when sg_len (derived from max_segs) is zero. If sg_len is zero, we return an error and print an error message, allowing host driver developers to identify and fix incorrect max_segs configuration.
This is a defensive measure that ensures the MMC core fails gracefully when host drivers provide invalid max_segs values, rather than crashing with a page fault.
{
"affected": [],
"aliases": [
"CVE-2026-98884"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-23T12:18:22Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmmc: core: Add validation for host-provided max_segs\n\nThe max_segs field is of type unsigned short, and if a host driver\nsets an excessively large value, it may be truncated to zero. This\ncan cause mmc_alloc_sg() to call kmalloc_objs() with a zero size\nallocation request, which leads to undefined behavior.\n\nUnder the SLUB allocator, kmalloc(0) returns a special pointer\n(ZERO_SIZE_PTR). The subsequent \u0027if (sg)\u0027 check will evaluate to\ntrue, and sg_init_table() will then attempt to access invalid memory,\nresulting in a crash:\n\ndwmmc_rockchip 2a310000.mmc: Successfully tuned phase to 133\nmmc1: new UHS-I speed SDR104 SDHC card at address aaaa\nUnable to handle kernel paging request at virtual address 0000001ffffffff0\nMem abort info:\nESR = 0x0000000096000004\nEC = 0x25: DABT (current EL), IL = 32 bits\nSET = 0, FnV = 0\nEA = 0, S1PTW = 0\nFSC = 0x04: level 0 translation fault\nData abort info:\nISV = 0, ISS = 0x00000004, ISS2 = 0x00000000\nCM = 0, WnR = 0, TnD = 0, TagAccess = 0\nGCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0\nuser pgtable: 4k pages, 48-bit VAs, pgdp=0000000102c88000\n[0000001ffffffff0] pgd=0000000000000000, p4d=0000000000000000\nInternal error: Oops: 0000000096000004 [#1] SMP\nModules linked in:\nCPU: 2 UID: 0 PID: 102 Comm: kworker/2:1 Not tainted 7.0.0-rc6-next-20260331-00013-g4d93c25963c5-dirty #80 PREEMPT\nHardware name: Rockchip RK3576 EVB V10 Board (DT)\nWorkqueue: events_freezable mmc_rescan\npstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)\npc : sg_init_table+0x2c/0x50\nlr : sg_init_table+0x24/0x50\nsp : ffff8000837db710\nx29: ffff8000837db710 x28: 000000000000c000 x27: 0000000000000300\nx26: 0000000000000000 x25: 0000000000000040 x24: ffff0000c46a0000\nx23: 0000000000000000 x22: ffff0000c0c73c00 x21: 0000000000000010\nx20: 0000000000000010 x19: 0000000000000000 x18: 000000000000002c\nx17: 0000000000000000 x16: 0000000000000001 x15: 0000000000000000\nx14: 0000000000000400 x13: ffff8000837dc000 x12: 0000000000000000\nx11: ffff0000c0c73ca0 x10: 0000000000000040 x9 : 459ec1f0abbdbb00\nx8 : 0000001fffffffe0 x7 : 0000000000000000 x6 : 000000000000003f\nx5 : 0000000000035579 x4 : 0000000000000901 x3 : 0000000000000000\nx2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000010\nCall trace:\nsg_init_table+0x2c/0x50 (P)\nmmc_mq_init_request+0x64/0x90\nblk_mq_alloc_map_and_rqs+0x3ac/0x480\nblk_mq_alloc_set_map_and_rqs+0x98/0x1e0\nblk_mq_alloc_tag_set+0x1c0/0x290\nmmc_init_queue+0x120/0x370\nmmc_blk_alloc_req+0x150/0x420\n\nTo prevent this, add a validation check in mmc_mq_init_request() to\ndetect when sg_len (derived from max_segs) is zero. If sg_len is zero,\nwe return an error and print an error message, allowing host driver\ndevelopers to identify and fix incorrect max_segs configuration.\n\nThis is a defensive measure that ensures the MMC core fails gracefully\nwhen host drivers provide invalid max_segs values, rather than crashing\nwith a page fault.",
"id": "GHSA-f98w-wx7q-xjvq",
"modified": "2026-10-23T12:31:36Z",
"published": "2026-10-23T12:31:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98884"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/03f5a16ec85beebabd5ab5e67ac1527f87908ded"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3e0483e93a8be320f70a1ff68d835f7f015af311"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9cca3c0c1472d6204ef8a78a6e7b3afe9610b22e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a8283f7d93f0d9336b15618b9665279ff6944319"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b037c2f7794aa01ee2a00e43c29645fd2dd2dfb9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c465608bd25d7f8565be7817a6a36a5d69f8aa14"
}
],
"schema_version": "1.4.0",
"severity": []
}
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