From f45812cc23fb74bef62d4eb8a69fe7218f4b9f2a Mon Sep 17 00:00:00 2001 From: Tim Schumacher Date: Fri, 26 Jan 2024 17:25:23 +0100 Subject: efivarfs: Request at most 512 bytes for variable names Work around a quirk in a few old (2011-ish) UEFI implementations, where a call to `GetNextVariableName` with a buffer size larger than 512 bytes will always return EFI_INVALID_PARAMETER. There is some lore around EFI variable names being up to 1024 bytes in size, but this has no basis in the UEFI specification, and the upper bounds are typically platform specific, and apply to the entire variable (name plus payload). Given that Linux does not permit creating files with names longer than NAME_MAX (255) bytes, 512 bytes (== 256 UTF-16 characters) is a reasonable limit. Cc: # 6.1+ Signed-off-by: Tim Schumacher Signed-off-by: Ard Biesheuvel --- fs/efivarfs/vars.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) (limited to 'fs') diff --git a/fs/efivarfs/vars.c b/fs/efivarfs/vars.c index 114ff0fd4e55..2ad377818d0f 100644 --- a/fs/efivarfs/vars.c +++ b/fs/efivarfs/vars.c @@ -373,7 +373,7 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *, struct list_head *), void *data, bool duplicates, struct list_head *head) { - unsigned long variable_name_size = 1024; + unsigned long variable_name_size = 512; efi_char16_t *variable_name; efi_status_t status; efi_guid_t vendor_guid; @@ -390,12 +390,13 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *, goto free; /* - * Per EFI spec, the maximum storage allocated for both - * the variable name and variable data is 1024 bytes. + * A small set of old UEFI implementations reject sizes + * above a certain threshold, the lowest seen in the wild + * is 512. */ do { - variable_name_size = 1024; + variable_name_size = 512; status = efivar_get_next_variable(&variable_name_size, variable_name, @@ -432,9 +433,13 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *, break; case EFI_NOT_FOUND: break; + case EFI_BUFFER_TOO_SMALL: + pr_warn("efivars: Variable name size exceeds maximum (%lu > 512)\n", + variable_name_size); + status = EFI_NOT_FOUND; + break; default: - printk(KERN_WARNING "efivars: get_next_variable: status=%lx\n", - status); + pr_warn("efivars: get_next_variable: status=%lx\n", status); status = EFI_NOT_FOUND; break; } -- cgit v1.2.3-58-ga151 From 9ca01c7adf3993044f59934082087ebb9f7df6d5 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Sat, 24 Feb 2024 18:45:41 +0100 Subject: efivarfs: Drop redundant cleanup on fill_super() failure Al points out that kill_sb() will be called if efivarfs_fill_super() fails and so there is no point in cleaning up the efivar entry list. Reported-by: Alexander Viro Signed-off-by: Ard Biesheuvel --- fs/efivarfs/super.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'fs') diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index 6038dd39367a..210daac79748 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -343,12 +343,7 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc) if (err) return err; - err = efivar_init(efivarfs_callback, (void *)sb, true, - &sfi->efivarfs_list); - if (err) - efivar_entry_iter(efivarfs_destroy, &sfi->efivarfs_list, NULL); - - return err; + return efivar_init(efivarfs_callback, sb, true, &sfi->efivarfs_list); } static int efivarfs_get_tree(struct fs_context *fc) -- cgit v1.2.3-58-ga151 From 2ce507f57ba9c78c080d4a050ebdc97263239de8 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Sat, 24 Feb 2024 18:48:14 +0100 Subject: efivarfs: Drop 'duplicates' bool parameter on efivar_init() The 'duplicates' bool argument is always true when efivar_init() is called from its only caller so let's just drop it instead. Signed-off-by: Ard Biesheuvel --- fs/efivarfs/internal.h | 2 +- fs/efivarfs/super.c | 2 +- fs/efivarfs/vars.c | 6 ++---- 3 files changed, 4 insertions(+), 6 deletions(-) (limited to 'fs') diff --git a/fs/efivarfs/internal.h b/fs/efivarfs/internal.h index 169252e6dc46..f7206158ee81 100644 --- a/fs/efivarfs/internal.h +++ b/fs/efivarfs/internal.h @@ -38,7 +38,7 @@ struct efivar_entry { int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *, struct list_head *), - void *data, bool duplicates, struct list_head *head); + void *data, struct list_head *head); int efivar_entry_add(struct efivar_entry *entry, struct list_head *head); void __efivar_entry_add(struct efivar_entry *entry, struct list_head *head); diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index 210daac79748..bb14462f6d99 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -343,7 +343,7 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc) if (err) return err; - return efivar_init(efivarfs_callback, sb, true, &sfi->efivarfs_list); + return efivar_init(efivarfs_callback, sb, &sfi->efivarfs_list); } static int efivarfs_get_tree(struct fs_context *fc) diff --git a/fs/efivarfs/vars.c b/fs/efivarfs/vars.c index 2ad377818d0f..4d722af1014f 100644 --- a/fs/efivarfs/vars.c +++ b/fs/efivarfs/vars.c @@ -361,7 +361,6 @@ static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid, * efivar_init - build the initial list of EFI variables * @func: callback function to invoke for every variable * @data: function-specific data to pass to @func - * @duplicates: error if we encounter duplicates on @head? * @head: initialised head of variable list * * Get every EFI variable from the firmware and invoke @func. @func @@ -371,7 +370,7 @@ static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid, */ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *, struct list_head *), - void *data, bool duplicates, struct list_head *head) + void *data, struct list_head *head) { unsigned long variable_name_size = 512; efi_char16_t *variable_name; @@ -414,8 +413,7 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *, * we'll ever see a different variable name, * and may end up looping here forever. */ - if (duplicates && - variable_is_present(variable_name, &vendor_guid, + if (variable_is_present(variable_name, &vendor_guid, head)) { dup_variable_bug(variable_name, &vendor_guid, variable_name_size); -- cgit v1.2.3-58-ga151