| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20250625231838.1897085-27-pasha.tatashin@soleen.com>
Date: Wed, 25 Jun 2025 23:18:13 +0000
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: pratyush@...nel.org,
jasonmiu@...gle.com,
graf@...zon.com,
changyuanl@...gle.com,
pasha.tatashin@...een.com,
rppt@...nel.org,
dmatlack@...gle.com,
rientjes@...gle.com,
corbet@....net,
rdunlap@...radead.org,
ilpo.jarvinen@...ux.intel.com,
kanie@...ux.alibaba.com,
ojeda@...nel.org,
aliceryhl@...gle.com,
masahiroy@...nel.org,
akpm@...ux-foundation.org,
tj@...nel.org,
yoann.congal@...le.fr,
mmaurer@...gle.com,
roman.gushchin@...ux.dev,
chenridong@...wei.com,
axboe@...nel.dk,
mark.rutland@....com,
jannh@...gle.com,
vincent.guittot@...aro.org,
hannes@...xchg.org,
dan.j.williams@...el.com,
david@...hat.com,
joel.granados@...nel.org,
rostedt@...dmis.org,
anna.schumaker@...cle.com,
song@...nel.org,
zhangguopeng@...inos.cn,
linux@...ssschuh.net,
linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org,
linux-mm@...ck.org,
gregkh@...uxfoundation.org,
tglx@...utronix.de,
mingo@...hat.com,
bp@...en8.de,
dave.hansen@...ux.intel.com,
x86@...nel.org,
hpa@...or.com,
rafael@...nel.org,
dakr@...nel.org,
bartosz.golaszewski@...aro.org,
cw00.choi@...sung.com,
myungjoo.ham@...sung.com,
yesanishhere@...il.com,
Jonathan.Cameron@...wei.com,
quic_zijuhu@...cinc.com,
aleksander.lobakin@...el.com,
ira.weiny@...el.com,
andriy.shevchenko@...ux.intel.com,
leon@...nel.org,
lukas@...ner.de,
bhelgaas@...gle.com,
wagi@...nel.org,
djeffery@...hat.com,
stuart.w.hayes@...il.com,
ptyadav@...zon.de,
lennart@...ttering.net,
brauner@...nel.org,
linux-api@...r.kernel.org,
linux-fsdevel@...r.kernel.org
Subject: [PATCH v1 26/32] mm: shmem: allow freezing inode mapping
From: Pratyush Yadav <ptyadav@...zon.de>
To prepare a shmem inode for live update via the Live Update
Orchestrator (LUO), its index -> folio mappings must be serialized. Once
the mappings are serialized, they cannot change since it would cause the
serialized data to become inconsistent. This can be done by pinning the
folios to avoid migration, and by making sure no folios can be added to
or removed from the inode.
While mechanisms to pin folios already exist, the only way to stop
folios being added or removed are the grow and shrink file seals. But
file seals come with their own semantics, one of which is that they
can't be removed. This doesn't work with liveupdate since it can be
cancelled or error out, which would need the seals to be removed and the
file's normal functionality to be restored.
Introduce SHMEM_F_MAPPING_FROZEN to indicate this instead. It is
internal to shmem and is not directly exposed to userspace. It functions
similar to F_SEAL_GROW | F_SEAL_SHRINK, but additionally disallows hole
punching, and can be removed.
Signed-off-by: Pratyush Yadav <ptyadav@...zon.de>
Signed-off-by: Pasha Tatashin <pahsa.tatashin@...een.com>
---
include/linux/shmem_fs.h | 17 +++++++++++++++++
mm/shmem.c | 12 +++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 578a5f3d1935..1dd2aad0986b 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -22,6 +22,14 @@
#define SHMEM_F_NORESERVE BIT(0)
/* Disallow swapping. */
#define SHMEM_F_LOCKED BIT(1)
+/*
+ * Disallow growing, shrinking, or hole punching in the inode. Combined with
+ * folio pinning, makes sure the inode's mapping stays fixed.
+ *
+ * In some ways similar to F_SEAL_GROW | F_SEAL_SHRINK, but can be removed and
+ * isn't directly visible to userspace.
+ */
+#define SHMEM_F_MAPPING_FROZEN BIT(2)
struct shmem_inode_info {
spinlock_t lock;
@@ -183,6 +191,15 @@ static inline bool shmem_file(struct file *file)
return shmem_mapping(file->f_mapping);
}
+/* Must be called with inode lock taken exclusive. */
+static inline void shmem_i_mapping_freeze(struct inode *inode, bool freeze)
+{
+ if (freeze)
+ SHMEM_I(inode)->flags |= SHMEM_F_MAPPING_FROZEN;
+ else
+ SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN;
+}
+
/*
* If fallocate(FALLOC_FL_KEEP_SIZE) has been used, there may be pages
* beyond i_size's notion of EOF, which fallocate has committed to reserving:
diff --git a/mm/shmem.c b/mm/shmem.c
index 953d89f62882..bd54300be9df 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1297,7 +1297,8 @@ static int shmem_setattr(struct mnt_idmap *idmap,
loff_t newsize = attr->ia_size;
/* protected by i_rwsem */
- if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
+ if ((info->flags & SHMEM_F_MAPPING_FROZEN) ||
+ (newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
(newsize > oldsize && (info->seals & F_SEAL_GROW)))
return -EPERM;
@@ -3291,6 +3292,10 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
return -EPERM;
}
+ if (unlikely((info->flags & SHMEM_F_MAPPING_FROZEN) &&
+ pos + len > inode->i_size))
+ return -EPERM;
+
ret = shmem_get_folio(inode, index, pos + len, &folio, SGP_WRITE);
if (ret)
return ret;
@@ -3664,6 +3669,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
inode_lock(inode);
+ if (info->flags & SHMEM_F_MAPPING_FROZEN) {
+ error = -EPERM;
+ goto out;
+ }
+
if (mode & FALLOC_FL_PUNCH_HOLE) {
struct address_space *mapping = file->f_mapping;
loff_t unmap_start = round_up(offset, PAGE_SIZE);
--
2.50.0.727.gbf7dc18ff4-goog
Powered by blists - more mailing lists