Several crypto user API contexts and requests allocated with
sock_kmalloc() were left uninitialized, relying on callers to
set fields explicitly. This resulted in the use of uninitialized
data in certain error paths or when new fields are added in the
future.
The ACVP patches also contain two user-space interface files:
algif_kpp.c and algif_akcipher.c. These too rely on proper
initialization of their context structures.
A particular issue has been observed with the newly added
'inflight' variable introduced in af_alg_ctx by commit:
67b164a871af ("crypto: af_alg - Disallow multiple in-flight AIO requests")
Because the context is not memset to zero after allocation,
the inflight variable has contained garbage values. As a result,
af_alg_alloc_areq() has incorrectly returned -EBUSY randomly when
the garbage value was interpreted as true:
https://github.com/gregkh/linux/blame/master/crypto/af_alg.c#L1209
The check directly tests ctx->inflight without explicitly
comparing against true/false. Since inflight is only ever set to
true or false later, an uninitialized value has triggered
-EBUSY failures. Zero-initializing memory allocated with
sock_kmalloc() ensures inflight and other fields start in a known
state, removing random issues caused by uninitialized data.
Fixes: fe869cdb89c9 ("crypto: algif_hash - User-space interface for hash operations")
Fixes: 5afdfd22e6ba ("crypto: algif_rng - add random number generator support")
Fixes: 2d97591ef43d ("crypto: af_alg - consolidation of duplicate code")
Fixes: 99bd99d3e3a7 ("crypto: algif_skcipher - Fix stream cipher chaining")
Fixes: 67b164a871af ("crypto: af_alg - Disallow multiple in-flight AIO requests")
Cc: stable(a)vger.kernel.org
Signed-off-by: Shivani Agarwal <shivani.agarwal(a)broadcom.com>
---
crypto/af_alg.c | 5 ++---
crypto/algif_hash.c | 3 +--
crypto/algif_rng.c | 3 +--
crypto/algif_skcipher.c | 1 +
4 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index ca6fdcc6c54a..6c271e55f44d 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1212,15 +1212,14 @@ struct af_alg_async_req *af_alg_alloc_areq(struct sock *sk,
if (unlikely(!areq))
return ERR_PTR(-ENOMEM);
+ memset(areq, 0, areqlen);
+
ctx->inflight = true;
areq->areqlen = areqlen;
areq->sk = sk;
areq->first_rsgl.sgl.sgt.sgl = areq->first_rsgl.sgl.sgl;
- areq->last_rsgl = NULL;
INIT_LIST_HEAD(&areq->rsgl_list);
- areq->tsgl = NULL;
- areq->tsgl_entries = 0;
return areq;
}
diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index e3f1a4852737..4d3dfc60a16a 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -416,9 +416,8 @@ static int hash_accept_parent_nokey(void *private, struct sock *sk)
if (!ctx)
return -ENOMEM;
- ctx->result = NULL;
+ memset(ctx, 0, len);
ctx->len = len;
- ctx->more = false;
crypto_init_wait(&ctx->wait);
ask->private = ctx;
diff --git a/crypto/algif_rng.c b/crypto/algif_rng.c
index 10c41adac3b1..1a86e40c8372 100644
--- a/crypto/algif_rng.c
+++ b/crypto/algif_rng.c
@@ -248,9 +248,8 @@ static int rng_accept_parent(void *private, struct sock *sk)
if (!ctx)
return -ENOMEM;
+ memset(ctx, 0, len);
ctx->len = len;
- ctx->addtl = NULL;
- ctx->addtl_len = 0;
/*
* No seeding done at that point -- if multiple accepts are
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 125d395c5e00..f4ce5473324f 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -70,6 +70,7 @@ static int algif_skcipher_export(struct sock *sk, struct skcipher_request *req)
if (!ctx->state)
return -ENOMEM;
+ memset(ctx->state, 0, statesize);
err = crypto_skcipher_export(req, ctx->state);
if (err) {
sock_kzfree_s(sk, ctx->state, statesize);
--
2.40.4
The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025092142-easiness-blatancy-23af@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd(a)google.com>
Date: Mon, 8 Sep 2025 15:23:15 -0700
Subject: [PATCH] mm: folio_may_be_lru_cached() unless folio_test_large()
mm/swap.c and mm/mlock.c agree to drain any per-CPU batch as soon as a
large folio is added: so collect_longterm_unpinnable_folios() just wastes
effort when calling lru_add_drain[_all]() on a large folio.
But although there is good reason not to batch up PMD-sized folios, we
might well benefit from batching a small number of low-order mTHPs (though
unclear how that "small number" limitation will be implemented).
So ask if folio_may_be_lru_cached() rather than !folio_test_large(), to
insulate those particular checks from future change. Name preferred to
"folio_is_batchable" because large folios can well be put on a batch: it's
just the per-CPU LRU caches, drained much later, which need care.
Marked for stable, to counter the increase in lru_add_drain_all()s from
"mm/gup: check ref_count instead of lru before migration".
Link: https://lkml.kernel.org/r/57d2eaf8-3607-f318-e0c5-be02dce61ad0@google.com
Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region")
Signed-off-by: Hugh Dickins <hughd(a)google.com>
Suggested-by: David Hildenbrand <david(a)redhat.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar(a)kernel.org>
Cc: Axel Rasmussen <axelrasmussen(a)google.com>
Cc: Chris Li <chrisl(a)kernel.org>
Cc: Christoph Hellwig <hch(a)infradead.org>
Cc: Jason Gunthorpe <jgg(a)ziepe.ca>
Cc: Johannes Weiner <hannes(a)cmpxchg.org>
Cc: John Hubbard <jhubbard(a)nvidia.com>
Cc: Keir Fraser <keirf(a)google.com>
Cc: Konstantin Khlebnikov <koct9i(a)gmail.com>
Cc: Li Zhe <lizhe.67(a)bytedance.com>
Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Cc: Peter Xu <peterx(a)redhat.com>
Cc: Rik van Riel <riel(a)surriel.com>
Cc: Shivank Garg <shivankg(a)amd.com>
Cc: Vlastimil Babka <vbabka(a)suse.cz>
Cc: Wei Xu <weixugc(a)google.com>
Cc: Will Deacon <will(a)kernel.org>
Cc: yangge <yangge1116(a)126.com>
Cc: Yuanchu Xie <yuanchu(a)google.com>
Cc: Yu Zhao <yuzhao(a)google.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 2fe6ed2cc3fd..7012a0f758d8 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -385,6 +385,16 @@ void folio_add_lru_vma(struct folio *, struct vm_area_struct *);
void mark_page_accessed(struct page *);
void folio_mark_accessed(struct folio *);
+static inline bool folio_may_be_lru_cached(struct folio *folio)
+{
+ /*
+ * Holding PMD-sized folios in per-CPU LRU cache unbalances accounting.
+ * Holding small numbers of low-order mTHP folios in per-CPU LRU cache
+ * will be sensible, but nobody has implemented and tested that yet.
+ */
+ return !folio_test_large(folio);
+}
+
extern atomic_t lru_disable_count;
static inline bool lru_cache_disabled(void)
diff --git a/mm/gup.c b/mm/gup.c
index b47066a54f52..0bc4d140fc07 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2307,13 +2307,13 @@ static unsigned long collect_longterm_unpinnable_folios(
continue;
}
- if (drained == 0 &&
+ if (drained == 0 && folio_may_be_lru_cached(folio) &&
folio_ref_count(folio) !=
folio_expected_ref_count(folio) + 1) {
lru_add_drain();
drained = 1;
}
- if (drained == 1 &&
+ if (drained == 1 && folio_may_be_lru_cached(folio) &&
folio_ref_count(folio) !=
folio_expected_ref_count(folio) + 1) {
lru_add_drain_all();
diff --git a/mm/mlock.c b/mm/mlock.c
index a1d93ad33c6d..bb0776f5ef7c 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -255,7 +255,7 @@ void mlock_folio(struct folio *folio)
folio_get(folio);
if (!folio_batch_add(fbatch, mlock_lru(folio)) ||
- folio_test_large(folio) || lru_cache_disabled())
+ !folio_may_be_lru_cached(folio) || lru_cache_disabled())
mlock_folio_batch(fbatch);
local_unlock(&mlock_fbatch.lock);
}
@@ -278,7 +278,7 @@ void mlock_new_folio(struct folio *folio)
folio_get(folio);
if (!folio_batch_add(fbatch, mlock_new(folio)) ||
- folio_test_large(folio) || lru_cache_disabled())
+ !folio_may_be_lru_cached(folio) || lru_cache_disabled())
mlock_folio_batch(fbatch);
local_unlock(&mlock_fbatch.lock);
}
@@ -299,7 +299,7 @@ void munlock_folio(struct folio *folio)
*/
folio_get(folio);
if (!folio_batch_add(fbatch, folio) ||
- folio_test_large(folio) || lru_cache_disabled())
+ !folio_may_be_lru_cached(folio) || lru_cache_disabled())
mlock_folio_batch(fbatch);
local_unlock(&mlock_fbatch.lock);
}
diff --git a/mm/swap.c b/mm/swap.c
index 6ae2d5680574..b74ebe865dd9 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -192,7 +192,7 @@ static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
local_lock(&cpu_fbatches.lock);
if (!folio_batch_add(this_cpu_ptr(fbatch), folio) ||
- folio_test_large(folio) || lru_cache_disabled())
+ !folio_may_be_lru_cached(folio) || lru_cache_disabled())
folio_batch_move_lru(this_cpu_ptr(fbatch), move_fn);
if (disable_irq)
devm_kcalloc() may fail. mt8365_afe_suspend() uses afe->reg_back_up
unconditionally after allocation and writes afe->reg_back_up[i], which
can lead to a NULL pointer dereference under low-memory conditions.
Add a NULL check and bail out with -ENOMEM, making sure to disable the
main clock via the existing error path to keep clock state balanced.
Fixes: e1991d102bc2 ("ASoC: mediatek: mt8365: Add the AFE driver support")
Cc: stable(a)vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244(a)gmail.com>
---
sound/soc/mediatek/mt8365/mt8365-afe-pcm.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/sound/soc/mediatek/mt8365/mt8365-afe-pcm.c b/sound/soc/mediatek/mt8365/mt8365-afe-pcm.c
index 10793bbe9275..eaeb14e1fce9 100644
--- a/sound/soc/mediatek/mt8365/mt8365-afe-pcm.c
+++ b/sound/soc/mediatek/mt8365/mt8365-afe-pcm.c
@@ -1979,6 +1979,10 @@ static int mt8365_afe_suspend(struct device *dev)
afe->reg_back_up =
devm_kcalloc(dev, afe->reg_back_up_list_num,
sizeof(unsigned int), GFP_KERNEL);
+ if (!afe->reg_back_up) {
+ mt8365_afe_disable_main_clk(afe);
+ return -ENOMEM;
+ }
for (i = 0; i < afe->reg_back_up_list_num; i++)
regmap_read(regmap, afe->reg_back_up_list[i],
--
2.43.0
The fmh_gpib driver contains a device reference count leak in
fmh_gpib_attach_impl() where driver_find_device() increases the
reference count of the device by get_device() when matching but this
reference is not properly decreased. Add put_device() in
fmh_gpib_detach(), which ensures that the reference count of the
device is correctly managed.
Found by code review.
Cc: stable(a)vger.kernel.org
Fixes: 8e4841a0888c ("staging: gpib: Add Frank Mori Hess FPGA PCI GPIB driver")
Signed-off-by: Ma Ke <make24(a)iscas.ac.cn>
---
Changes in v3:
- deleted the redundant put_device() to avoid double free as suggestions;
Changes in v2:
- modified the free operations as suggestions. Thanks for dan carpenter's instructions.
---
drivers/staging/gpib/fmh_gpib/fmh_gpib.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/staging/gpib/fmh_gpib/fmh_gpib.c b/drivers/staging/gpib/fmh_gpib/fmh_gpib.c
index 4138f3d2bae7..efce01b39b9b 100644
--- a/drivers/staging/gpib/fmh_gpib/fmh_gpib.c
+++ b/drivers/staging/gpib/fmh_gpib/fmh_gpib.c
@@ -1517,6 +1517,11 @@ void fmh_gpib_detach(struct gpib_board *board)
resource_size(e_priv->gpib_iomem_res));
}
fmh_gpib_generic_detach(board);
+
+ if (board->dev) {
+ put_device(board->dev);
+ board->dev = NULL;
+ }
}
static int fmh_gpib_pci_attach_impl(struct gpib_board *board,
--
2.17.1
wcd934x_codec_parse_data() contains a device reference count leak in
of_slim_get_device() where device_find_child() increases the reference
count of the device but this reference is not properly decreased in
the success path. Add put_device() in wcd934x_codec_parse_data() and
add devm_add_action_or_reset() in the probe function, which ensures
that the reference count of the device is correctly managed.
Memory leak in regmap_init_slimbus() as the allocated regmap is not
released when the device is removed. Using devm_regmap_init_slimbus()
instead of regmap_init_slimbus() to ensure automatic regmap cleanup on
device removal.
Calling path: of_slim_get_device() -> of_find_slim_device() ->
device_find_child(). As comment of device_find_child() says, 'NOTE:
you will need to drop the reference with put_device() after use.'.
Found by code review.
Cc: stable(a)vger.kernel.org
Fixes: a61f3b4f476e ("ASoC: wcd934x: add support to wcd9340/wcd9341 codec")
Signed-off-by: Ma Ke <make24(a)iscas.ac.cn>
---
Changes in v3:
- added a wrapper function due to the warning report from kernel test robot;
Changes in v2:
- modified the handling in the success path and fixed the memory leak for regmap as suggestions.
---
sound/soc/codecs/wcd934x.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/sound/soc/codecs/wcd934x.c b/sound/soc/codecs/wcd934x.c
index 1bb7e1dc7e6b..d9d8cf64977a 100644
--- a/sound/soc/codecs/wcd934x.c
+++ b/sound/soc/codecs/wcd934x.c
@@ -5831,6 +5831,15 @@ static const struct snd_soc_component_driver wcd934x_component_drv = {
.endianness = 1,
};
+static void wcd934x_put_device_action(void *data)
+{
+ struct device *dev = data;
+
+ if (dev) {
+ put_device(dev);
+ }
+}
+
static int wcd934x_codec_parse_data(struct wcd934x_codec *wcd)
{
struct device *dev = &wcd->sdev->dev;
@@ -5847,11 +5856,13 @@ static int wcd934x_codec_parse_data(struct wcd934x_codec *wcd)
return dev_err_probe(dev, -EINVAL, "Unable to get SLIM Interface device\n");
slim_get_logical_addr(wcd->sidev);
- wcd->if_regmap = regmap_init_slimbus(wcd->sidev,
+ wcd->if_regmap = devm_regmap_init_slimbus(wcd->sidev,
&wcd934x_ifc_regmap_config);
- if (IS_ERR(wcd->if_regmap))
+ if (IS_ERR(wcd->if_regmap)) {
+ put_device(&wcd->sidev->dev);
return dev_err_probe(dev, PTR_ERR(wcd->if_regmap),
"Failed to allocate ifc register map\n");
+ }
of_property_read_u32(dev->parent->of_node, "qcom,dmic-sample-rate",
&wcd->dmic_sample_rate);
@@ -5893,6 +5904,10 @@ static int wcd934x_codec_probe(struct platform_device *pdev)
if (ret)
return ret;
+ ret = devm_add_action_or_reset(dev, wcd934x_put_device_action, &wcd->sidev->dev);
+ if (ret)
+ return ret;
+
/* set default rate 9P6MHz */
regmap_update_bits(wcd->regmap, WCD934X_CODEC_RPM_CLK_MCLK_CFG,
WCD934X_CODEC_RPM_CLK_MCLK_CFG_MCLK_MASK,
--
2.17.1
The quilt patch titled
Subject: selftests/mm: skip soft-dirty tests when CONFIG_MEM_SOFT_DIRTY is disabled
has been removed from the -mm tree. Its filename was
selftests-mm-skip-soft-dirty-tests-when-config_mem_soft_dirty-is-disabled.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Lance Yang <lance.yang(a)linux.dev>
Subject: selftests/mm: skip soft-dirty tests when CONFIG_MEM_SOFT_DIRTY is disabled
Date: Wed, 17 Sep 2025 21:31:37 +0800
The madv_populate and soft-dirty kselftests currently fail on systems
where CONFIG_MEM_SOFT_DIRTY is disabled.
Introduce a new helper softdirty_supported() into vm_util.c/h to ensure
tests are properly skipped when the feature is not enabled.
Link: https://lkml.kernel.org/r/20250917133137.62802-1-lance.yang@linux.dev
Fixes: 9f3265db6ae8 ("selftests: vm: add test for Soft-Dirty PTE bit")
Signed-off-by: Lance Yang <lance.yang(a)linux.dev>
Acked-by: David Hildenbrand <david(a)redhat.com>
Suggested-by: David Hildenbrand <david(a)redhat.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Shuah Khan <shuah(a)kernel.org>
Cc: Gabriel Krisman Bertazi <krisman(a)collabora.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
tools/testing/selftests/mm/madv_populate.c | 21 +------------------
tools/testing/selftests/mm/soft-dirty.c | 5 +++-
tools/testing/selftests/mm/vm_util.c | 17 +++++++++++++++
tools/testing/selftests/mm/vm_util.h | 1
4 files changed, 24 insertions(+), 20 deletions(-)
--- a/tools/testing/selftests/mm/madv_populate.c~selftests-mm-skip-soft-dirty-tests-when-config_mem_soft_dirty-is-disabled
+++ a/tools/testing/selftests/mm/madv_populate.c
@@ -264,23 +264,6 @@ static void test_softdirty(void)
munmap(addr, SIZE);
}
-static int system_has_softdirty(void)
-{
- /*
- * There is no way to check if the kernel supports soft-dirty, other
- * than by writing to a page and seeing if the bit was set. But the
- * tests are intended to check that the bit gets set when it should, so
- * doing that check would turn a potentially legitimate fail into a
- * skip. Fortunately, we know for sure that arm64 does not support
- * soft-dirty. So for now, let's just use the arch as a corse guide.
- */
-#if defined(__aarch64__)
- return 0;
-#else
- return 1;
-#endif
-}
-
int main(int argc, char **argv)
{
int nr_tests = 16;
@@ -288,7 +271,7 @@ int main(int argc, char **argv)
pagesize = getpagesize();
- if (system_has_softdirty())
+ if (softdirty_supported())
nr_tests += 5;
ksft_print_header();
@@ -300,7 +283,7 @@ int main(int argc, char **argv)
test_holes();
test_populate_read();
test_populate_write();
- if (system_has_softdirty())
+ if (softdirty_supported())
test_softdirty();
err = ksft_get_fail_cnt();
--- a/tools/testing/selftests/mm/soft-dirty.c~selftests-mm-skip-soft-dirty-tests-when-config_mem_soft_dirty-is-disabled
+++ a/tools/testing/selftests/mm/soft-dirty.c
@@ -200,8 +200,11 @@ int main(int argc, char **argv)
int pagesize;
ksft_print_header();
- ksft_set_plan(15);
+ if (!softdirty_supported())
+ ksft_exit_skip("soft-dirty is not support\n");
+
+ ksft_set_plan(15);
pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY);
if (pagemap_fd < 0)
ksft_exit_fail_msg("Failed to open %s\n", PAGEMAP_FILE_PATH);
--- a/tools/testing/selftests/mm/vm_util.c~selftests-mm-skip-soft-dirty-tests-when-config_mem_soft_dirty-is-disabled
+++ a/tools/testing/selftests/mm/vm_util.c
@@ -449,6 +449,23 @@ bool check_vmflag_pfnmap(void *addr)
return check_vmflag(addr, "pf");
}
+bool softdirty_supported(void)
+{
+ char *addr;
+ bool supported = false;
+ const size_t pagesize = getpagesize();
+
+ /* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */
+ addr = mmap(0, pagesize, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+ if (!addr)
+ ksft_exit_fail_msg("mmap failed\n");
+
+ supported = check_vmflag(addr, "sd");
+ munmap(addr, pagesize);
+ return supported;
+}
+
/*
* Open an fd at /proc/$pid/maps and configure procmap_out ready for
* PROCMAP_QUERY query. Returns 0 on success, or an error code otherwise.
--- a/tools/testing/selftests/mm/vm_util.h~selftests-mm-skip-soft-dirty-tests-when-config_mem_soft_dirty-is-disabled
+++ a/tools/testing/selftests/mm/vm_util.h
@@ -104,6 +104,7 @@ bool find_vma_procmap(struct procmap_fd
int close_procmap(struct procmap_fd *procmap);
int write_sysfs(const char *file_path, unsigned long val);
int read_sysfs(const char *file_path, unsigned long *val);
+bool softdirty_supported(void);
static inline int open_self_procmap(struct procmap_fd *procmap_out)
{
_
Patches currently in -mm which might be from lance.yang(a)linux.dev are
hung_task-fix-warnings-caused-by-unaligned-lock-pointers.patch
mm-thp-fix-mte-tag-mismatch-when-replacing-zero-filled-subpages.patch
The quilt patch titled
Subject: kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths
has been removed from the -mm tree. Its filename was
fix-the-racy-usage-of-task_locktsk-group_leader-in-sys_prlimit64-paths.patch
This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Oleg Nesterov <oleg(a)redhat.com>
Subject: kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths
Date: Mon, 15 Sep 2025 14:09:17 +0200
The usage of task_lock(tsk->group_leader) in sys_prlimit64()->do_prlimit()
path is very broken.
sys_prlimit64() does get_task_struct(tsk) but this only protects task_struct
itself. If tsk != current and tsk is not a leader, this process can exit/exec
and task_lock(tsk->group_leader) may use the already freed task_struct.
Another problem is that sys_prlimit64() can race with mt-exec which changes
->group_leader. In this case do_prlimit() may take the wrong lock, or (worse)
->group_leader may change between task_lock() and task_unlock().
Change sys_prlimit64() to take tasklist_lock when necessary. This is not
nice, but I don't see a better fix for -stable.
Link: https://lkml.kernel.org/r/20250915120917.GA27702@redhat.com
Fixes: 18c91bb2d872 ("prlimit: do not grab the tasklist_lock")
Signed-off-by: Oleg Nesterov <oleg(a)redhat.com>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: Jiri Slaby <jirislaby(a)kernel.org>
Cc: Mateusz Guzik <mjguzik(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
kernel/sys.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
--- a/kernel/sys.c~fix-the-racy-usage-of-task_locktsk-group_leader-in-sys_prlimit64-paths
+++ a/kernel/sys.c
@@ -1734,6 +1734,7 @@ SYSCALL_DEFINE4(prlimit64, pid_t, pid, u
struct rlimit old, new;
struct task_struct *tsk;
unsigned int checkflags = 0;
+ bool need_tasklist;
int ret;
if (old_rlim)
@@ -1760,8 +1761,25 @@ SYSCALL_DEFINE4(prlimit64, pid_t, pid, u
get_task_struct(tsk);
rcu_read_unlock();
- ret = do_prlimit(tsk, resource, new_rlim ? &new : NULL,
- old_rlim ? &old : NULL);
+ need_tasklist = !same_thread_group(tsk, current);
+ if (need_tasklist) {
+ /*
+ * Ensure we can't race with group exit or de_thread(),
+ * so tsk->group_leader can't be freed or changed until
+ * read_unlock(tasklist_lock) below.
+ */
+ read_lock(&tasklist_lock);
+ if (!pid_alive(tsk))
+ ret = -ESRCH;
+ }
+
+ if (!ret) {
+ ret = do_prlimit(tsk, resource, new_rlim ? &new : NULL,
+ old_rlim ? &old : NULL);
+ }
+
+ if (need_tasklist)
+ read_unlock(&tasklist_lock);
if (!ret && old_rlim) {
rlim_to_rlim64(&old, &old64);
_
Patches currently in -mm which might be from oleg(a)redhat.com are