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Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1vkkD3-00H3b9-MS; Tue, 27 Jan 2026 14:38:26 +0000 From: Breno Leitao Date: Tue, 27 Jan 2026 06:37:36 -0800 Subject: [PATCH v6 1/4] kho: add size parameter to kho_add_subtree() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260127-kho-v6-1-56f9396681c2@debian.org> References: <20260127-kho-v6-0-56f9396681c2@debian.org> In-Reply-To: <20260127-kho-v6-0-56f9396681c2@debian.org> To: Alexander Graf , Mike Rapoport , Pasha Tatashin , Pratyush Yadav Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, usamaarif642@gmail.com, rmikey@meta.com, clm@fb.com, riel@surriel.com, Breno Leitao , SeongJae Park , kernel-team@meta.com X-Mailer: b4 0.15-dev-f4305 X-Developer-Signature: v=1; a=openpgp-sha256; l=9092; i=leitao@debian.org; h=from:subject:message-id; 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This assumption will break if a caller passes arbitrary data instead of an FDT. When CONFIG_KEXEC_HANDOVER_DEBUGFS is enabled, kho_debugfs_fdt_add() calls __kho_debugfs_fdt_add(), which executes: f->wrapper.size = fdt_totalsize(fdt); Fix this by adding an explicit size parameter to kho_add_subtree() so callers specify the blob size. This allows subtrees to contain arbitrary data formats, not just FDTs. Update all callers: - memblock.c: use fdt_totalsize(fdt) - luo_core.c: use fdt_totalsize(fdt_out) - test_kho.c: use fdt_totalsize() - kexec_handover.c (root fdt): use fdt_totalsize(kho_out.fdt) Also update kho_in_debugfs_init() to compute sizes using fdt_totalsize() for the root and sub-FDTs it processes, since these are known to be actual FDT blobs. Suggested-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) Signed-off-by: Breno Leitao --- include/linux/kexec_handover.h | 4 ++-- kernel/liveupdate/kexec_handover.c | 8 +++++--- kernel/liveupdate/kexec_handover_debugfs.c | 15 +++++++++------ kernel/liveupdate/kexec_handover_internal.h | 5 +++-- kernel/liveupdate/luo_core.c | 3 ++- lib/test_kho.c | 3 ++- mm/memblock.c | 2 +- 7 files changed, 24 insertions(+), 16 deletions(-) diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h index ac4129d1d7416..abb1d324f42d0 100644 --- a/include/linux/kexec_handover.h +++ b/include/linux/kexec_handover.h @@ -32,7 +32,7 @@ void kho_restore_free(void *mem); struct folio *kho_restore_folio(phys_addr_t phys); struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages); void *kho_restore_vmalloc(const struct kho_vmalloc *preservation); -int kho_add_subtree(const char *name, void *fdt); +int kho_add_subtree(const char *name, void *fdt, size_t size); void kho_remove_subtree(void *fdt); int kho_retrieve_subtree(const char *name, phys_addr_t *phys); @@ -97,7 +97,7 @@ static inline void *kho_restore_vmalloc(const struct kho_vmalloc *preservation) return NULL; } -static inline int kho_add_subtree(const char *name, void *fdt) +static inline int kho_add_subtree(const char *name, void *fdt, size_t size) { return -EOPNOTSUPP; } diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 8a2b2a7e50fc6..ad2da9e4e6a04 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -726,6 +726,7 @@ static void __init kho_reserve_scratch(void) * kho_add_subtree - record the physical address of a sub FDT in KHO root tree. * @name: name of the sub tree. * @fdt: the sub tree blob. + * @size: size of the blob in bytes. * * Creates a new child node named @name in KHO root FDT and records * the physical address of @fdt. The pages of @fdt must also be preserved @@ -737,7 +738,7 @@ static void __init kho_reserve_scratch(void) * * Return: 0 on success, error code on failure */ -int kho_add_subtree(const char *name, void *fdt) +int kho_add_subtree(const char *name, void *fdt, size_t size) { phys_addr_t phys = virt_to_phys(fdt); void *root_fdt = kho_out.fdt; @@ -762,7 +763,7 @@ int kho_add_subtree(const char *name, void *fdt) if (err < 0) goto out_pack; - WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false)); + WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, size, false)); out_pack: fdt_pack(root_fdt); @@ -1402,7 +1403,8 @@ static __init int kho_init(void) } WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt", - kho_out.fdt, true)); + kho_out.fdt, + fdt_totalsize(kho_out.fdt), true)); return 0; diff --git a/kernel/liveupdate/kexec_handover_debugfs.c b/kernel/liveupdate/kexec_handover_debugfs.c index 2abbf62ba9424..64970c88c483c 100644 --- a/kernel/liveupdate/kexec_handover_debugfs.c +++ b/kernel/liveupdate/kexec_handover_debugfs.c @@ -24,7 +24,7 @@ struct fdt_debugfs { }; static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir, - const char *name, const void *fdt) + const char *name, const void *fdt, size_t size) { struct fdt_debugfs *f; struct dentry *file; @@ -34,7 +34,7 @@ static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir, return -ENOMEM; f->wrapper.data = (void *)fdt; - f->wrapper.size = fdt_totalsize(fdt); + f->wrapper.size = size; file = debugfs_create_blob(name, 0400, dir, &f->wrapper); if (IS_ERR(file)) { @@ -49,7 +49,7 @@ static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir, } int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name, - const void *fdt, bool root) + const void *fdt, size_t size, bool root) { struct dentry *dir; @@ -58,7 +58,7 @@ int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name, else dir = dbg->sub_fdt_dir; - return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt); + return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt, size); } void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt) @@ -130,7 +130,8 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt) goto err_rmdir; } - err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt); + err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt, + fdt_totalsize(fdt)); if (err) goto err_rmdir; @@ -138,6 +139,7 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt) int len = 0; const char *name = fdt_get_name(fdt, child, NULL); const u64 *fdt_phys; + void *sub_fdt; fdt_phys = fdt_getprop(fdt, child, "fdt", &len); if (!fdt_phys) @@ -147,8 +149,9 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt) name, len); continue; } + sub_fdt = phys_to_virt(*fdt_phys); err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name, - phys_to_virt(*fdt_phys)); + sub_fdt, fdt_totalsize(sub_fdt)); if (err) { pr_warn("failed to add fdt %s to debugfs: %pe\n", name, ERR_PTR(err)); diff --git a/kernel/liveupdate/kexec_handover_internal.h b/kernel/liveupdate/kexec_handover_internal.h index 0202c85ad14f9..a51f97f0fa0e6 100644 --- a/kernel/liveupdate/kexec_handover_internal.h +++ b/kernel/liveupdate/kexec_handover_internal.h @@ -30,7 +30,7 @@ int kho_debugfs_init(void); void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt); int kho_out_debugfs_init(struct kho_debugfs *dbg); int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name, - const void *fdt, bool root); + const void *fdt, size_t size, bool root); void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt); #else static inline int kho_debugfs_init(void) { return 0; } @@ -38,7 +38,8 @@ static inline void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt) { } static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; } static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name, - const void *fdt, bool root) { return 0; } + const void *fdt, size_t size, + bool root) { return 0; } static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt) { } #endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */ diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c index dda7bb57d421c..a4721813dd994 100644 --- a/kernel/liveupdate/luo_core.c +++ b/kernel/liveupdate/luo_core.c @@ -172,7 +172,8 @@ static int __init luo_fdt_setup(void) if (err) goto exit_free; - err = kho_add_subtree(LUO_FDT_KHO_ENTRY_NAME, fdt_out); + err = kho_add_subtree(LUO_FDT_KHO_ENTRY_NAME, fdt_out, + fdt_totalsize(fdt_out)); if (err) goto exit_free; luo_global.fdt_out = fdt_out; diff --git a/lib/test_kho.c b/lib/test_kho.c index a20fafaf9846b..f2d7d9108cf41 100644 --- a/lib/test_kho.c +++ b/lib/test_kho.c @@ -143,7 +143,8 @@ static int kho_test_preserve(struct kho_test_state *state) if (err) goto err_unpreserve_data; - err = kho_add_subtree(KHO_TEST_FDT, folio_address(state->fdt)); + err = kho_add_subtree(KHO_TEST_FDT, folio_address(state->fdt), + fdt_totalsize(folio_address(state->fdt))); if (err) goto err_unpreserve_data; diff --git a/mm/memblock.c b/mm/memblock.c index b3ddfdec7a809..91d4162eec63f 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -2510,7 +2510,7 @@ static int __init prepare_kho_fdt(void) if (err) goto err_unpreserve_fdt; - err = kho_add_subtree(MEMBLOCK_KHO_FDT, fdt); + err = kho_add_subtree(MEMBLOCK_KHO_FDT, fdt, fdt_totalsize(fdt)); if (err) goto err_unpreserve_fdt; -- 2.47.3