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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-16 17:23:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-16 17:23:57 -0700
commitffbc93768e9d3a3dafdd90124b1244b4723d30e8 (patch)
tree2f4fe646933a734f9cab8ccb8b723b6050f6f640 /fs
parentff58155ca4fa7e931f34d948fa09fe14c6a66116 (diff)
parent76fafbfffb447d2a5a95d5a9486b0217c00f9785 (diff)
Merge tag 'flex-array-conversions-5.8-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux
Pull flexible-array member conversions from Gustavo A. R. Silva: "Replace zero-length arrays with flexible-array members. Notice that all of these patches have been baking in linux-next for two development cycles now. There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. C99 introduced “flexible array members”, which lacks a numeric size for the array declaration entirely: struct something { size_t count; struct foo items[]; }; This is the way the kernel expects dynamically sized trailing elements to be declared. It allows the compiler to generate errors when the flexible array does not occur last in the structure, which helps to prevent some kind of undefined behavior[3] bugs from being inadvertently introduced to the codebase. It also allows the compiler to correctly analyze array sizes (via sizeof(), CONFIG_FORTIFY_SOURCE, and CONFIG_UBSAN_BOUNDS). For instance, there is no mechanism that warns us that the following application of the sizeof() operator to a zero-length array always results in zero: struct something { size_t count; struct foo items[0]; }; struct something *instance; instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL); instance->count = count; size = sizeof(instance->items) * instance->count; memcpy(instance->items, source, size); At the last line of code above, size turns out to be zero, when one might have thought it represents the total size in bytes of the dynamic memory recently allocated for the trailing array items. Here are a couple examples of this issue[4][5]. Instead, flexible array members have incomplete type, and so the sizeof() operator may not be applied[6], so any misuse of such operators will be immediately noticed at build time. The cleanest and least error-prone way to implement this is through the use of a flexible array member: struct something { size_t count; struct foo items[]; }; struct something *instance; instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL); instance->count = count; size = sizeof(instance->items[0]) * instance->count; memcpy(instance->items, source, size); instead" [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") [4] commit f2cd32a443da ("rndis_wlan: Remove logically dead code") [5] commit ab91c2a89f86 ("tpm: eventlog: Replace zero-length array with flexible-array member") [6] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html * tag 'flex-array-conversions-5.8-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux: (41 commits) w1: Replace zero-length array with flexible-array tracing/probe: Replace zero-length array with flexible-array soc: ti: Replace zero-length array with flexible-array tifm: Replace zero-length array with flexible-array dmaengine: tegra-apb: Replace zero-length array with flexible-array stm class: Replace zero-length array with flexible-array Squashfs: Replace zero-length array with flexible-array ASoC: SOF: Replace zero-length array with flexible-array ima: Replace zero-length array with flexible-array sctp: Replace zero-length array with flexible-array phy: samsung: Replace zero-length array with flexible-array RxRPC: Replace zero-length array with flexible-array rapidio: Replace zero-length array with flexible-array media: pwc: Replace zero-length array with flexible-array firmware: pcdp: Replace zero-length array with flexible-array oprofile: Replace zero-length array with flexible-array block: Replace zero-length array with flexible-array tools/testing/nvdimm: Replace zero-length array with flexible-array libata: Replace zero-length array with flexible-array kprobes: Replace zero-length array with flexible-array ...
Diffstat (limited to 'fs')
-rw-r--r--fs/aio.c2
-rw-r--r--fs/jffs2/nodelist.h2
-rw-r--r--fs/jffs2/summary.h4
-rw-r--r--fs/squashfs/squashfs_fs.h16
4 files changed, 12 insertions, 12 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 7ecddc2f38db..91e7cc4a9f17 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -67,7 +67,7 @@ struct aio_ring {
unsigned header_length; /* size of aio_ring */
- struct io_event io_events[0];
+ struct io_event io_events[];
}; /* 128 bytes + ring size */
/*
diff --git a/fs/jffs2/nodelist.h b/fs/jffs2/nodelist.h
index 0637271f3770..8ff4d1a1e774 100644
--- a/fs/jffs2/nodelist.h
+++ b/fs/jffs2/nodelist.h
@@ -259,7 +259,7 @@ struct jffs2_full_dirent
uint32_t ino; /* == zero for unlink */
unsigned int nhash;
unsigned char type;
- unsigned char name[0];
+ unsigned char name[];
};
/*
diff --git a/fs/jffs2/summary.h b/fs/jffs2/summary.h
index 60207a2ae952..e4131cb1f1d4 100644
--- a/fs/jffs2/summary.h
+++ b/fs/jffs2/summary.h
@@ -61,7 +61,7 @@ struct jffs2_sum_dirent_flash
jint32_t ino; /* == zero for unlink */
uint8_t nsize; /* dirent name size */
uint8_t type; /* dirent type */
- uint8_t name[0]; /* dirent name */
+ uint8_t name[]; /* dirent name */
} __attribute__((packed));
struct jffs2_sum_xattr_flash
@@ -117,7 +117,7 @@ struct jffs2_sum_dirent_mem
jint32_t ino; /* == zero for unlink */
uint8_t nsize; /* dirent name size */
uint8_t type; /* dirent type */
- uint8_t name[0]; /* dirent name */
+ uint8_t name[]; /* dirent name */
} __attribute__((packed));
struct jffs2_sum_xattr_mem
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index 7187bd1a30ea..8d64edb80ebf 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -262,7 +262,7 @@ struct squashfs_dir_index {
__le32 index;
__le32 start_block;
__le32 size;
- unsigned char name[0];
+ unsigned char name[];
};
struct squashfs_base_inode {
@@ -327,7 +327,7 @@ struct squashfs_symlink_inode {
__le32 inode_number;
__le32 nlink;
__le32 symlink_size;
- char symlink[0];
+ char symlink[];
};
struct squashfs_reg_inode {
@@ -341,7 +341,7 @@ struct squashfs_reg_inode {
__le32 fragment;
__le32 offset;
__le32 file_size;
- __le16 block_list[0];
+ __le16 block_list[];
};
struct squashfs_lreg_inode {
@@ -358,7 +358,7 @@ struct squashfs_lreg_inode {
__le32 fragment;
__le32 offset;
__le32 xattr;
- __le16 block_list[0];
+ __le16 block_list[];
};
struct squashfs_dir_inode {
@@ -389,7 +389,7 @@ struct squashfs_ldir_inode {
__le16 i_count;
__le16 offset;
__le32 xattr;
- struct squashfs_dir_index index[0];
+ struct squashfs_dir_index index[];
};
union squashfs_inode {
@@ -410,7 +410,7 @@ struct squashfs_dir_entry {
__le16 inode_number;
__le16 type;
__le16 size;
- char name[0];
+ char name[];
};
struct squashfs_dir_header {
@@ -428,12 +428,12 @@ struct squashfs_fragment_entry {
struct squashfs_xattr_entry {
__le16 type;
__le16 size;
- char data[0];
+ char data[];
};
struct squashfs_xattr_val {
__le32 vsize;
- char value[0];
+ char value[];
};
struct squashfs_xattr_id {