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CVE-2022-49771

Estado: AnalizadaMedia (4.7)—

In the Linux kernel, the following vulnerability has been resolved:

dm ioctl: fix misbehavior if list_versions races with module loading

__list_versions will first estimate the required space using the "dm_target_iterate(list_version_get_needed, &needed)" call and then will fill the space using the "dm_target_iterate(list_version_get_info, &iter_info)" call. Each of these calls locks the targets using the "down_read(&_lock)" and "up_read(&_lock)" calls, however between the first and second "dm_target_iterate" there is no lock held and the target modules can be loaded at this point, so the second "dm_target_iterate" call may need more space than what was the first "dm_target_iterate" returned.

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The code tries to handle this overflow (see the beginning of list_version_get_info), however this handling is incorrect.

The code sets "param->data_size = param->data_start + needed" and "iter_info.end = (char *)vers+len" - "needed" is the size returned by the first dm_target_iterate call; "len" is the size of the buffer allocated by userspace.

"len" may be greater than "needed"; in this case, the code will write up to "len" bytes into the buffer, however param->data_size is set to "needed", so it may write data past the param->data_size value. The ioctl interface copies only up to param->data_size into userspace, thus part of the result will be truncated.

Fix this bug by setting "iter_info.end = (char *)vers + needed;" - this guarantees that the second "dm_target_iterate" call will write only up to the "needed" buffer and it will exit with "DM_BUFFER_FULL_FLAG" if it overflows the "needed" space - in this case, userspace will allocate a larger buffer and retry.

Note that there is also a bug in list_version_get_needed - we need to add "strlen(tt->name) + 1" to the needed size, not "strlen(tt->name)".

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndm ioctl: fix misbehavior if list_versions races with module loading\n\n__list_versions will first estimate the required space using the\n\"dm_target_iterate(list_version_get_needed, &needed)\" call and then will\nfill the space using the \"dm_target_iterate(list_version_get_info,\n&iter_info)\" call. Each of these calls locks the targets using the\n\"down_read(&_lock)\" and \"up_read(&_lock)\" calls, however between the first\nand second \"dm_target_iterate\" there is no lock held and the target\nmodules can be loaded at this point, so the second \"dm_target_iterate\"\ncall may need more space than what was the first \"dm_target_iterate\"\nreturned.\n\nThe code tries to handle this overflow (see the beginning of\nlist_version_get_info), however this handling is incorrect.\n\nThe code sets \"param->data_size = param->data_start + needed\" and\n\"iter_info.end = (char *)vers+len\" - \"needed\" is the size returned by the\nfirst dm_target_iterate call; \"len\" is the size of the buffer allocated by\nuserspace.\n\n\"len\" may be greater than \"needed\"; in this case, the code will write up\nto \"len\" bytes into the buffer, however param->data_size is set to\n\"needed\", so it may write data past the param->data_size value. The ioctl\ninterface copies only up to param->data_size into userspace, thus part of\nthe result will be truncated.\n\nFix this bug by setting \"iter_info.end = (char *)vers + needed;\" - this\nguarantees that the second \"dm_target_iterate\" call will write only up to\nthe \"needed\" buffer and it will exit with \"DM_BUFFER_FULL_FLAG\" if it\noverflows the \"needed\" space - in this case, userspace will allocate a\nlarger buffer and retry.\n\nNote that there is also a bug in list_version_get_needed - we need to add\n\"strlen(tt->name) + 1\" to the needed size, not \"strlen(tt->name)\"."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: dm ioctl: se corrige el comportamiento incorrecto si list_versions se acelera al cargar módulos. __list_versions primero estimará el espacio requerido mediante la llamada \"dm_target_iterate(list_version_get_needed, &needed)\" y luego llenará el espacio mediante la llamada \"dm_target_iterate(list_version_get_info, &iter_info)\". Cada una de estas llamadas bloquea los destinos mediante las llamadas \"down_read(&_lock)\" y \"up_read(&_lock)\". Sin embargo, entre la primera y la segunda llamada \"dm_target_iterate\" no se mantiene el bloqueo y los módulos de destino se pueden cargar en este punto, por lo que la segunda llamada \"dm_target_iterate\" podría necesitar más espacio que el devuelto por la primera llamada \"dm_target_iterate\". El código intenta gestionar este desbordamiento (véase el comienzo de list_version_get_info), pero esta gestión es incorrecta. El código establece \"param->data_size = param->data_start + needed\" y \"iter_info.end = (char *)vers+len\": \"needed\" es el tamaño devuelto por la primera llamada a dm_target_iterate; \"len\" es el tamaño del búfer asignado por el espacio de usuario. \"len\" puede ser mayor que \"needed\"; en este caso, el código escribirá hasta \"len\" bytes en el búfer; sin embargo, param->data_size se establece en \"needed\", por lo que podría escribir datos que superen el valor de param->data_size. La interfaz ioctl solo copia hasta param->data_size en el espacio de usuario, por lo que parte del resultado se truncará. Corrija este error estableciendo \"iter_info.end = (char *)vers + needed;\" Esto garantiza que la segunda llamada \"dm_target_iterate\" solo escriba hasta el búfer necesario y finalice con \"DM_BUFFER_FULL_FLAG\" si se desborda dicho espacio. En este caso, el espacio de usuario asignará un búfer mayor y reintentará. Tenga en cuenta que también hay un error en list_version_get_needed: debemos agregar \"strlen(tt->name) + 1\" al tamaño necesario, no \"strlen(tt->name)\"."
    }
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  "lastModified": "2026-06-17T05:19:06.477",
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