In the Linux kernel, the following vulnerability has been resolved:
padata: Fix refcnt handling in padata_free_shell()
In a high-load arm64 environment, the pcrypt_aead01 test in LTP can lead
to system UAF (Use-After-Free) issues. Due to the lengthy analysis of
the pcrypt_aead01 function call, I’ll describe the problem scenario
using a simplified model:
Suppose there’s a user of padata named user_function
that adheres to
the padata requirement of calling padata_free_shell
after serial()
has been invoked, as demonstrated in the following code:
struct request {
struct padata_priv padata;
struct completion *done;
};
void parallel(struct padata_priv *padata) {
do_something();
}
void serial(struct padata_priv *padata) {
struct request *request = container_of(padata,
struct request,
padata);
complete(request->done);
}
void user_function() {
DECLARE_COMPLETION(done)
padata->parallel = parallel;
padata->serial = serial;
padata_do_parallel();
wait_for_completion(&done);
padata_free_shell();
}
In the corresponding padata.c file, there’s the following code:
static void padata_serial_worker(struct work_struct *serial_work) {
...
cnt = 0;
while (!list_empty(&local_list)) {
...
padata->serial(padata);
cnt++;
}
local_bh_enable();
if (refcount_sub_and_test(cnt, &pd->refcnt))
padata_free_pd(pd);
}
Because of the high system load and the accumulation of unexecuted
softirq at this moment, local_bh_enable()
in padata takes longer
to execute than usual. Subsequently, when accessing pd->refcnt
,
pd
has already been released by padata_free_shell()
, resulting
in a UAF issue with pd->refcnt
.
The fix is straightforward: add refcount_dec_and_test
before calling
padata_free_pd
in padata_free_shell
.
[
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"kernel/padata.c"
],
"versions": [
{
"version": "07928d9bfc81",
"lessThan": "41aad9d69539",
"status": "affected",
"versionType": "git"
},
{
"version": "07928d9bfc81",
"lessThan": "0dd34a7ad395",
"status": "affected",
"versionType": "git"
},
{
"version": "07928d9bfc81",
"lessThan": "c7c26d0ef5d2",
"status": "affected",
"versionType": "git"
},
{
"version": "07928d9bfc81",
"lessThan": "1e901bcb8af1",
"status": "affected",
"versionType": "git"
},
{
"version": "07928d9bfc81",
"lessThan": "1734a79e9519",
"status": "affected",
"versionType": "git"
},
{
"version": "07928d9bfc81",
"lessThan": "7ddc21e317b3",
"status": "affected",
"versionType": "git"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"kernel/padata.c"
],
"versions": [
{
"version": "5.6",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.6",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "5.10.201",
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "5.15.139",
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.1.63",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.5.12",
"lessThanOrEqual": "6.5.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.6.2",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "6.7",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
]
git.kernel.org/stable/c/0dd34a7ad395dbcf6ae60e48e9786050e25b9bc5
git.kernel.org/stable/c/1734a79e951914f1db2c65e635012a35db1c674b
git.kernel.org/stable/c/1e901bcb8af19416b65f5063a4af7996e5a51d7f
git.kernel.org/stable/c/41aad9d6953984d134fc50f631f24ef476875d4d
git.kernel.org/stable/c/7ddc21e317b360c3444de3023bcc83b85fabae2f
git.kernel.org/stable/c/c7c26d0ef5d20f00dbb2ae3befcabbe0efa77275