CVE-2022-49648
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
tracing/histograms: Fix memory leak problem
This reverts commit 46bbe5c671e06f070428b9be142cc4ee5cedebac.
These two frees don't act on same name, so there was no "double free" problem before. Conversely, after that commit, we get a "memory leak" problem because the above "N-th var_defs.name" is not freed.
If enable CONFIG_DEBUG_KMEMLEAK and inject a fault at where the N-th var_defs.expr allocated, then execute on shell like: $ echo 'hist:key=call_site:val=$v1,$v2:v1=bytes_req,v2=bytes_alloc' > \ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
Detalles técnicos trazas, registros y código del informe original
As commit 46bbe5c671e0 ("tracing: fix double free") said, the
"double free" problem reported by clang static analyzer is:
> In parse_var_defs() if there is a problem allocating
> var_defs.expr, the earlier var_defs.name is freed.
> This free is duplicated by free_var_defs() which frees
> the rest of the list.
However, if there is a problem allocating N-th var_defs.expr:
+ in parse_var_defs(), the freed 'earlier var_defs.name' is
actually the N-th var_defs.name;
+ then in free_var_defs(), the names from 0th to (N-1)-th are freed;
IF ALLOCATING PROBLEM HAPPENED HERE!!! -+
\
|
0th 1th (N-1)-th N-th V
+-------------+-------------+-----+-------------+-----------
var_defs: | name | expr | name | expr | ... | name | expr | name | ///
+-------------+-------------+-----+-------------+-----------
Then kmemleak reports:
unreferenced object 0xffff8fb100ef3518 (size 8):
comm "bash", pid 196, jiffies 4295681690 (age 28.538s)
hex dump (first 8 bytes):
76 31 00 00 b1 8f ff ff v1......
backtrace:
[<0000000038fe4895>] kstrdup+0x2d/0x60
[<00000000c99c049a>] event_hist_trigger_parse+0x206f/0x20e0
[<00000000ae70d2cc>] trigger_process_regex+0xc0/0x110
[<0000000066737a4c>] event_trigger_write+0x75/0xd0
[<000000007341e40c>] vfs_write+0xbb/0x2a0
[<0000000087fde4c2>] ksys_write+0x59/0xd0
[<00000000581e9cdf>] do_syscall_64+0x3a/0x80
[<00000000cf3b065c>] entry_SYSCALL_64_after_hwframe+0x46/0xb0CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.27%
- Percentil entre todas las CVEs puntuadas: 18
- Fecha de la puntuación: 6/10/2026
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)
CWE
- CWE-401
- CWE-401
Referencias
- https://git.kernel.org/stable/c/22eeff55679d9e7c0f768c79bfbd83e2f8142d89
- https://git.kernel.org/stable/c/4d453eb5e1eec89971aa5b3262857ee26cfdffd3
- https://git.kernel.org/stable/c/78a1400c42ee11197eb1f0f85ba51df9a4fdfff0
- https://git.kernel.org/stable/c/7edc3945bdce9c39198a10d6129377a5c53559c2
- https://git.kernel.org/stable/c/eb622d5580b9e2ff694f62da6410618bd73853cb
- https://git.kernel.org/stable/c/ecc6dec12c33aa92c086cd702af9f544ddaf3c75
JSON original (NVD)
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing/histograms: Fix memory leak problem\n\nThis reverts commit 46bbe5c671e06f070428b9be142cc4ee5cedebac.\n\nAs commit 46bbe5c671e0 (\"tracing: fix double free\") said, the\n\"double free\" problem reported by clang static analyzer is:\n > In parse_var_defs() if there is a problem allocating\n > var_defs.expr, the earlier var_defs.name is freed.\n > This free is duplicated by free_var_defs() which frees\n > the rest of the list.\n\nHowever, if there is a problem allocating N-th var_defs.expr:\n + in parse_var_defs(), the freed 'earlier var_defs.name' is\n actually the N-th var_defs.name;\n + then in free_var_defs(), the names from 0th to (N-1)-th are freed;\n\n IF ALLOCATING PROBLEM HAPPENED HERE!!! -+\n \\\n |\n 0th 1th (N-1)-th N-th V\n +-------------+-------------+-----+-------------+-----------\nvar_defs: | name | expr | name | expr | ... | name | expr | name | ///\n +-------------+-------------+-----+-------------+-----------\n\nThese two frees don't act on same name, so there was no \"double free\"\nproblem before. Conversely, after that commit, we get a \"memory leak\"\nproblem because the above \"N-th var_defs.name\" is not freed.\n\nIf enable CONFIG_DEBUG_KMEMLEAK and inject a fault at where the N-th\nvar_defs.expr allocated, then execute on shell like:\n $ echo 'hist:key=call_site:val=$v1,$v2:v1=bytes_req,v2=bytes_alloc' > \\\n/sys/kernel/debug/tracing/events/kmem/kmalloc/trigger\n\nThen kmemleak reports:\n unreferenced object 0xffff8fb100ef3518 (size 8):\n comm \"bash\", pid 196, jiffies 4295681690 (age 28.538s)\n hex dump (first 8 bytes):\n 76 31 00 00 b1 8f ff ff v1......\n backtrace:\n [<0000000038fe4895>] kstrdup+0x2d/0x60\n [<00000000c99c049a>] event_hist_trigger_parse+0x206f/0x20e0\n [<00000000ae70d2cc>] trigger_process_regex+0xc0/0x110\n [<0000000066737a4c>] event_trigger_write+0x75/0xd0\n [<000000007341e40c>] vfs_write+0xbb/0x2a0\n [<0000000087fde4c2>] ksys_write+0x59/0xd0\n [<00000000581e9cdf>] do_syscall_64+0x3a/0x80\n [<00000000cf3b065c>] entry_SYSCALL_64_after_hwframe+0x46/0xb0"
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: tracing/histograms: Fix memory leak problem Esto revierte el commit 46bbe5c671e06f070428b9be142cc4ee5cedebac. Como decía el commit 46bbe5c671e0 (\"tracing: fix double free\"), el problema de \"doble liberación\" informado por el analizador estático de clang es: > En parse_var_defs(), si hay un problema al asignar var_defs.expr, se libera el var_defs.name anterior. > Esta liberación se duplica mediante free_var_defs(), que libera el resto de la lista. Sin embargo, si hay un problema al asignar la N-ésima var_defs.expr: + en parse_var_defs(), el 'var_defs.name anterior' liberado es en realidad el N-ésimo var_defs.name; + entonces en free_var_defs(), los nombres del 0 al (N-1)-ésimo se liberan; ¡SI SUCEDIÓ UN PROBLEMA DE ASIGNACIÓN AQUÍ!!! -+ \\ | 0th 1th (N-1)-th N-th V +-------------+-------------+-----+-------------+----------- var_defs: | name | expr | name | expr | ... | name | expr | name | /// +-------------+-------------+-----+-------------+----------- Estas dos liberaciones no actúan sobre el mismo nombre, por lo que antes no había un problema de \"doble liberación\". Por el contrario, después de esa confirmación, tenemos un problema de \"pérdida de memoria\" porque el \"N-ésimo var_defs.name\" anterior no se libera. Si habilita CONFIG_DEBUG_KMEMLEAK e inyecta un error en el lugar donde se asignó el N-ésimo var_defs.expr, entonces ejecute en el shell de esta manera: $ echo 'hist:key=call_site:val=$v1,$v2:v1=bytes_req,v2=bytes_alloc' > \\ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger Then kmemleak reports: unreferenced object 0xffff8fb100ef3518 (size 8): comm \"bash\", pid 196, jiffies 4295681690 (age 28.538s) hex dump (first 8 bytes): 76 31 00 00 b1 8f ff ff v1...... backtrace: [<0000000038fe4895>] kstrdup+0x2d/0x60 [<00000000c99c049a>] event_hist_trigger_parse+0x206f/0x20e0 [<00000000ae70d2cc>] trigger_process_regex+0xc0/0x110 [<0000000066737a4c>] event_trigger_write+0x75/0xd0 [<000000007341e40c>] vfs_write+0xbb/0x2a0 [<0000000087fde4c2>] ksys_write+0x59/0xd0 [<00000000581e9cdf>] do_syscall_64+0x3a/0x80 [<00000000cf3b065c>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 "
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