[PATCH] binfmt_flat: Remove shared library support

Eric W. Biederman
2022-04-20T14:58:19Z

In a recent discussion[1] it was reported that the binfmt_flat library
support was only ever used on m68k and even on m68k has not been used
in a very long time.

The structure of binfmt_flat is different from all of the other binfmt
implementations becasue of this shared library support and it made
life and code review more effort when I refactored the code in fs/exec.c.

Since in practice the code is dead remove the binfmt_flat shared libarary
support and make maintenance of the code easier.

[1] https://lkml.kernel.org/r/81788b56-5b15-7308-38c7-c7f2502c4e15@linux-m68k.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---

Can the binfmt_flat folks please verify that the shared library support
really isn't used?

Was binfmt_flat being enabled on arm and sh the mistake it looks like?

arch/arm/configs/lpc18xx_defconfig | 1 -
arch/arm/configs/mps2_defconfig | 1 -
arch/arm/configs/stm32_defconfig | 1 -
arch/arm/configs/vf610m4_defconfig | 1 -
arch/sh/configs/rsk7201_defconfig | 1 -
arch/sh/configs/rsk7203_defconfig | 1 -
arch/sh/configs/se7206_defconfig | 1 -
fs/Kconfig.binfmt | 6 -
fs/binfmt_flat.c | 190 ++++++-----------------------
9 files changed, 40 insertions(+), 163 deletions(-)

diff --git a/arch/arm/configs/lpc18xx_defconfig b/arch/arm/configs/lpc18xx_defconfig
index be882ea0eee4..688c9849eec8 100644
--- a/arch/arm/configs/lpc18xx_defconfig
+++ b/arch/arm/configs/lpc18xx_defconfig
@@ -30,7 +30,6 @@ CONFIG_ARM_APPENDED_DTB=y
# CONFIG_BLK_DEV_BSG is not set
CONFIG_BINFMT_FLAT=y
CONFIG_BINFMT_ZFLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
# CONFIG_COREDUMP is not set
CONFIG_NET=y
CONFIG_PACKET=y
diff --git a/arch/arm/configs/mps2_defconfig b/arch/arm/configs/mps2_defconfig
index 89f4a6ff30bd..c1e98e33a348 100644
--- a/arch/arm/configs/mps2_defconfig
+++ b/arch/arm/configs/mps2_defconfig
@@ -23,7 +23,6 @@ CONFIG_PREEMPT_VOLUNTARY=y
CONFIG_ZBOOT_ROM_TEXT=0x0
CONFIG_ZBOOT_ROM_BSS=0x0
CONFIG_BINFMT_FLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
# CONFIG_COREDUMP is not set
# CONFIG_SUSPEND is not set
CONFIG_NET=y
diff --git a/arch/arm/configs/stm32_defconfig b/arch/arm/configs/stm32_defconfig
index 551db328009d..71d6bfcf4551 100644
--- a/arch/arm/configs/stm32_defconfig
+++ b/arch/arm/configs/stm32_defconfig
@@ -28,7 +28,6 @@ CONFIG_ZBOOT_ROM_BSS=0x0
CONFIG_XIP_KERNEL=y
CONFIG_XIP_PHYS_ADDR=0x08008000
CONFIG_BINFMT_FLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
# CONFIG_COREDUMP is not set
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y
diff --git a/arch/arm/configs/vf610m4_defconfig b/arch/arm/configs/vf610m4_defconfig
index a89f035c3b01..70fdbfd83484 100644
--- a/arch/arm/configs/vf610m4_defconfig
+++ b/arch/arm/configs/vf610m4_defconfig
@@ -18,7 +18,6 @@ CONFIG_XIP_KERNEL=y
CONFIG_XIP_PHYS_ADDR=0x0f000080
CONFIG_BINFMT_FLAT=y
CONFIG_BINFMT_ZFLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
# CONFIG_SUSPEND is not set
# CONFIG_UEVENT_HELPER is not set
# CONFIG_STANDALONE is not set
diff --git a/arch/sh/configs/rsk7201_defconfig b/arch/sh/configs/rsk7201_defconfig
index e41526120be1..619c18699459 100644
--- a/arch/sh/configs/rsk7201_defconfig
+++ b/arch/sh/configs/rsk7201_defconfig
@@ -25,7 +25,6 @@ CONFIG_CMDLINE_OVERWRITE=y
CONFIG_CMDLINE="console=ttySC0,115200 earlyprintk=serial ignore_loglevel"
CONFIG_BINFMT_FLAT=y
CONFIG_BINFMT_ZFLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
CONFIG_PM=y
CONFIG_CPU_IDLE=y
# CONFIG_STANDALONE is not set
diff --git a/arch/sh/configs/rsk7203_defconfig b/arch/sh/configs/rsk7203_defconfig
index 6af08fa1ddf8..5a54e2b883f0 100644
--- a/arch/sh/configs/rsk7203_defconfig
+++ b/arch/sh/configs/rsk7203_defconfig
@@ -30,7 +30,6 @@ CONFIG_CMDLINE_OVERWRITE=y
CONFIG_CMDLINE="console=ttySC0,115200 earlyprintk=serial ignore_loglevel"
CONFIG_BINFMT_FLAT=y
CONFIG_BINFMT_ZFLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
CONFIG_PM=y
CONFIG_CPU_IDLE=y
CONFIG_NET=y
diff --git a/arch/sh/configs/se7206_defconfig b/arch/sh/configs/se7206_defconfig
index 601d062250d1..122216123e63 100644
--- a/arch/sh/configs/se7206_defconfig
+++ b/arch/sh/configs/se7206_defconfig
@@ -40,7 +40,6 @@ CONFIG_CMDLINE_OVERWRITE=y
CONFIG_CMDLINE="console=ttySC3,115200 ignore_loglevel earlyprintk=serial"
CONFIG_BINFMT_FLAT=y
CONFIG_BINFMT_ZFLAT=y
-CONFIG_BINFMT_SHARED_FLAT=y
CONFIG_BINFMT_MISC=y
CONFIG_NET=y
CONFIG_PACKET=y
diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 21c6332fa785..32dff7ba3dda 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -142,12 +142,6 @@ config BINFMT_ZFLAT
help
Support FLAT format compressed binaries

-config BINFMT_SHARED_FLAT
- bool "Enable shared FLAT support"
- depends on BINFMT_FLAT
- help
- Support FLAT shared libraries
-
config HAVE_AOUT
def_bool n

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 0ad2c7bbaddd..82e4412a9665 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -68,11 +68,7 @@
#define RELOC_FAILED 0xff00ff01 /* Relocation incorrect somewhere */
#define UNLOADED_LIB 0x7ff000ff /* Placeholder for unused library */

-#ifdef CONFIG_BINFMT_SHARED_FLAT
-#define MAX_SHARED_LIBS (4)
-#else
-#define MAX_SHARED_LIBS (1)
-#endif
+#define MAX_SHARED_LIBS (1)

#ifdef CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET
#define DATA_START_OFFSET_WORDS (0)
@@ -92,10 +88,6 @@ struct lib_info {
} lib_list[MAX_SHARED_LIBS];
};

-#ifdef CONFIG_BINFMT_SHARED_FLAT
-static int load_flat_shared_library(int id, struct lib_info *p);
-#endif
-
static int load_flat_binary(struct linux_binprm *);

static struct linux_binfmt flat_format = {
@@ -307,51 +299,18 @@ static int decompress_exec(struct linux_binprm *bprm, loff_t fpos, char *dst,
/****************************************************************************/

static unsigned long
-calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
+calc_reloc(unsigned long r, struct lib_info *p)
{
unsigned long addr;
- int id;
unsigned long start_brk;
unsigned long start_data;
unsigned long text_len;
unsigned long start_code;

-#ifdef CONFIG_BINFMT_SHARED_FLAT
- if (r == 0)
- id = curid; /* Relocs of 0 are always self referring */
- else {
- id = (r >> 24) & 0xff; /* Find ID for this reloc */
- r &= 0x00ffffff; /* Trim ID off here */
- }
- if (id >= MAX_SHARED_LIBS) {
- pr_err("reference 0x%lx to shared library %d", r, id);
- goto failed;
- }
- if (curid != id) {
- if (internalp) {
- pr_err("reloc address 0x%lx not in same module "
- "(%d != %d)", r, curid, id);
- goto failed;
- } else if (!p->lib_list[id].loaded &&
- load_flat_shared_library(id, p) < 0) {
- pr_err("failed to load library %d", id);
- goto failed;
- }
- /* Check versioning information (i.e. time stamps) */
- if (p->lib_list[id].build_date && p->lib_list[curid].build_date &&
- p->lib_list[curid].build_date < p->lib_list[id].build_date) {
- pr_err("library %d is younger than %d", id, curid);
- goto failed;
- }
- }
-#else
- id = 0;
-#endif
-
- start_brk = p->lib_list[id].start_brk;
- start_data = p->lib_list[id].start_data;
- start_code = p->lib_list[id].start_code;
- text_len = p->lib_list[id].text_len;
+ start_brk = p->lib_list[0].start_brk;
+ start_data = p->lib_list[0].start_data;
+ start_code = p->lib_list[0].start_code;
+ text_len = p->lib_list[0].text_len;

if (r > start_brk - start_data + text_len) {
pr_err("reloc outside program 0x%lx (0 - 0x%lx/0x%lx)",
@@ -419,7 +378,7 @@ static void old_reloc(unsigned long rl)
/****************************************************************************/

static int load_flat_file(struct linux_binprm *bprm,
- struct lib_info *libinfo, int id, unsigned long *extra_stack)
+ struct lib_info *libinfo, unsigned long *extra_stack)
{
struct flat_hdr *hdr;
unsigned long textpos, datapos, realdatastart;
@@ -471,14 +430,6 @@ static int load_flat_file(struct linux_binprm *bprm,
goto err;
}

- /* Don't allow old format executables to use shared libraries */
- if (rev == OLD_FLAT_VERSION && id != 0) {
- pr_err("shared libraries are not available before rev 0x%lx\n",
- FLAT_VERSION);
- ret = -ENOEXEC;
- goto err;
- }
-
/*
* fix up the flags for the older format, there were all kinds
* of endian hacks, this only works for the simple cases
@@ -529,15 +480,13 @@ static int load_flat_file(struct linux_binprm *bprm,
}

/* Flush all traces of the currently running executable */
- if (id == 0) {
- ret = begin_new_exec(bprm);
- if (ret)
- goto err;
+ ret = begin_new_exec(bprm);
+ if (ret)
+ goto err;

- /* OK, This is the point of no return */
- set_personality(PER_LINUX_32BIT);
- setup_new_exec(bprm);
- }
+ /* OK, This is the point of no return */
+ set_personality(PER_LINUX_32BIT);
+ setup_new_exec(bprm);

/*
* calculate the extra space we need to map in
@@ -717,42 +666,40 @@ static int load_flat_file(struct linux_binprm *bprm,
text_len -= sizeof(struct flat_hdr); /* the real code len */

/* The main program needs a little extra setup in the task structure */
- if (id == 0) {
- current->mm->start_code = start_code;
- current->mm->end_code = end_code;
- current->mm->start_data = datapos;
- current->mm->end_data = datapos + data_len;
- /*
- * set up the brk stuff, uses any slack left in data/bss/stack
- * allocation. We put the brk after the bss (between the bss
- * and stack) like other platforms.
- * Userspace code relies on the stack pointer starting out at
- * an address right at the end of a page.
- */
- current->mm->start_brk = datapos + data_len + bss_len;
- current->mm->brk = (current->mm->start_brk + 3) & ~3;
+ current->mm->start_code = start_code;
+ current->mm->end_code = end_code;
+ current->mm->start_data = datapos;
+ current->mm->end_data = datapos + data_len;
+ /*
+ * set up the brk stuff, uses any slack left in data/bss/stack
+ * allocation. We put the brk after the bss (between the bss
+ * and stack) like other platforms.
+ * Userspace code relies on the stack pointer starting out at
+ * an address right at the end of a page.
+ */
+ current->mm->start_brk = datapos + data_len + bss_len;
+ current->mm->brk = (current->mm->start_brk + 3) & ~3;
#ifndef CONFIG_MMU
- current->mm->context.end_brk = memp + memp_size - stack_len;
+ current->mm->context.end_brk = memp + memp_size - stack_len;
#endif
- }

if (flags & FLAT_FLAG_KTRACE) {
pr_info("Mapping is %lx, Entry point is %x, data_start is %x\n",
textpos, 0x00ffffff&ntohl(hdr->entry), ntohl(hdr->data_start));
pr_info("%s %s: TEXT=%lx-%lx DATA=%lx-%lx BSS=%lx-%lx\n",
- id ? "Lib" : "Load", bprm->filename,
+ "Load", bprm->filename,
start_code, end_code, datapos, datapos + data_len,
datapos + data_len, (datapos + data_len + bss_len + 3) & ~3);
}

/* Store the current module values into the global library structure */
- libinfo->lib_list[id].start_code = start_code;
- libinfo->lib_list[id].start_data = datapos;
- libinfo->lib_list[id].start_brk = datapos + data_len + bss_len;
- libinfo->lib_list[id].text_len = text_len;
- libinfo->lib_list[id].loaded = 1;
- libinfo->lib_list[id].entry = (0x00ffffff & ntohl(hdr->entry)) + textpos;
- libinfo->lib_list[id].build_date = ntohl(hdr->build_date);
+ libinfo->lib_list[0].start_code = start_code;
+ libinfo->lib_list[0].start_data = datapos;
+ libinfo->lib_list[0].start_brk = datapos + data_len + bss_len;
+ libinfo->lib_list[0].text_len = text_len;
+ libinfo->lib_list[0].loaded = 1;
+ libinfo->lib_list[0].entry = (0x00ffffff & ntohl(hdr->entry)) + textpos;
+ libinfo->lib_list[0].build_date = ntohl(hdr->build_date);

/*
* We just load the allocations into some temporary memory to
@@ -774,7 +721,7 @@ static int load_flat_file(struct linux_binprm *bprm,
if (rp_val == 0xffffffff)
break;
if (rp_val) {
- addr = calc_reloc(rp_val, libinfo, id, 0);
+ addr = calc_reloc(rp_val, libinfo);
if (addr == RELOC_FAILED) {
ret = -ENOEXEC;
goto err;
@@ -810,7 +757,7 @@ static int load_flat_file(struct linux_binprm *bprm,
return -EFAULT;
relval = ntohl(tmp);
addr = flat_get_relocate_addr(relval);
- rp = (u32 __user *)calc_reloc(addr, libinfo, id, 1);
+ rp = (u32 __user *)calc_reloc(addr, libinfo);
if (rp == (u32 __user *)RELOC_FAILED) {
ret = -ENOEXEC;
goto err;
@@ -833,7 +780,7 @@ static int load_flat_file(struct linux_binprm *bprm,
*/
addr = ntohl((__force __be32)addr);
}
- addr = calc_reloc(addr, libinfo, id, 0);
+ addr = calc_reloc(addr, libinfo);
if (addr == RELOC_FAILED) {
ret = -ENOEXEC;
goto err;
@@ -861,7 +808,7 @@ static int load_flat_file(struct linux_binprm *bprm,
/* zero the BSS, BRK and stack areas */
if (clear_user((void __user *)(datapos + data_len), bss_len +
(memp + memp_size - stack_len - /* end brk */
- libinfo->lib_list[id].start_brk) + /* start brk */
+ libinfo->lib_list[0].start_brk) + /* start brk */
stack_len))
return -EFAULT;

@@ -871,49 +818,6 @@ static int load_flat_file(struct linux_binprm *bprm,
}

-/****************************************************************************/
-#ifdef CONFIG_BINFMT_SHARED_FLAT
-
-/*
- * Load a shared library into memory. The library gets its own data
- * segment (including bss) but not argv/argc/environ.
- */
-
-static int load_flat_shared_library(int id, struct lib_info *libs)
-{
- /*
- * This is a fake bprm struct; only the members "buf", "file" and
- * "filename" are actually used.
- */
- struct linux_binprm bprm;
- int res;
- char buf[16];
- loff_t pos = 0;
-
- memset(&bprm, 0, sizeof(bprm));
-
- /* Create the file name */
- sprintf(buf, "/lib/lib%d.so", id);
-
- /* Open the file up */
- bprm.filename = buf;
- bprm.file = open_exec(bprm.filename);
- res = PTR_ERR(bprm.file);
- if (IS_ERR(bprm.file))
- return res;
-
- res = kernel_read(bprm.file, bprm.buf, BINPRM_BUF_SIZE, &pos);
-
- if (res >= 0)
- res = load_flat_file(&bprm, libs, id, NULL);
-
- allow_write_access(bprm.file);
- fput(bprm.file);
-
- return res;
-}
-
-#endif /* CONFIG_BINFMT_SHARED_FLAT */
/****************************************************************************/

/*
@@ -946,7 +850,7 @@ static int load_flat_binary(struct linux_binprm *bprm)
stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */
stack_len = ALIGN(stack_len, FLAT_STACK_ALIGN);

- res = load_flat_file(bprm, &libinfo, 0, &stack_len);
+ res = load_flat_file(bprm, &libinfo, &stack_len);
if (res < 0)
return res;

@@ -991,20 +895,6 @@ static int load_flat_binary(struct linux_binprm *bprm)
*/
start_addr = libinfo.lib_list[0].entry;

-#ifdef CONFIG_BINFMT_SHARED_FLAT
- for (i = MAX_SHARED_LIBS-1; i > 0; i--) {
- if (libinfo.lib_list[i].loaded) {
- /* Push previos first to call address */
- unsigned long __user *sp;
- current->mm->start_stack -= sizeof(unsigned long);
- sp = (unsigned long __user *)current->mm->start_stack;
- if (put_user(start_addr, sp))
- return -EFAULT;
- start_addr = libinfo.lib_list[i].entry;
- }
- }
-#endif
-
#ifdef FLAT_PLAT_INIT
FLAT_PLAT_INIT(regs);
#endif
--
2.35.3