[PATCH 1/3] ELF: delete "loc" variable

[PATCH 1/3] ELF: delete "loc" variable

[Alexey Dobriyan]

"loc" variable became just a wrapper for PT_INTERP ELF header after
main ELF header was moved to "bprm->buf". Delete it.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/binfmt_elf.c |   32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -698,15 +698,13 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long reloc_func_desc __maybe_unused = 0;
 	int executable_stack = EXSTACK_DEFAULT;
 	struct elfhdr *elf_ex = (struct elfhdr *)bprm->buf;
-	struct {
-		struct elfhdr interp_elf_ex;
-	} *loc;
+	struct elfhdr *interp_elf_ex;
 	struct arch_elf_state arch_state = INIT_ARCH_ELF_STATE;
 	struct mm_struct *mm;
 	struct pt_regs *regs;
 
-	loc = kmalloc(sizeof(*loc), GFP_KERNEL);
-	if (!loc) {
+	interp_elf_ex = kmalloc(sizeof(*interp_elf_ex), GFP_KERNEL);
+	if (!interp_elf_ex) {
 		retval = -ENOMEM;
 		goto out_ret;
 	}
@@ -771,8 +769,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		would_dump(bprm, interpreter);
 
 		/* Get the exec headers */
-		retval = elf_read(interpreter, &loc->interp_elf_ex,
-				  sizeof(loc->interp_elf_ex), 0);
+		retval = elf_read(interpreter, interp_elf_ex,
+				  sizeof(*interp_elf_ex), 0);
 		if (retval < 0)
 			goto out_free_dentry;
 
@@ -806,25 +804,25 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	if (interpreter) {
 		retval = -ELIBBAD;
 		/* Not an ELF interpreter */
-		if (memcmp(loc->interp_elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
+		if (memcmp(interp_elf_ex->e_ident, ELFMAG, SELFMAG) != 0)
 			goto out_free_dentry;
 		/* Verify the interpreter has a valid arch */
-		if (!elf_check_arch(&loc->interp_elf_ex) ||
-		    elf_check_fdpic(&loc->interp_elf_ex))
+		if (!elf_check_arch(interp_elf_ex) ||
+		    elf_check_fdpic(interp_elf_ex))
 			goto out_free_dentry;
 
 		/* Load the interpreter program headers */
-		interp_elf_phdata = load_elf_phdrs(&loc->interp_elf_ex,
+		interp_elf_phdata = load_elf_phdrs(interp_elf_ex,
 						   interpreter);
 		if (!interp_elf_phdata)
 			goto out_free_dentry;
 
 		/* Pass PT_LOPROC..PT_HIPROC headers to arch code */
 		elf_ppnt = interp_elf_phdata;
-		for (i = 0; i < loc->interp_elf_ex.e_phnum; i++, elf_ppnt++)
+		for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++)
 			switch (elf_ppnt->p_type) {
 			case PT_LOPROC ... PT_HIPROC:
-				retval = arch_elf_pt_proc(&loc->interp_elf_ex,
+				retval = arch_elf_pt_proc(interp_elf_ex,
 							  elf_ppnt, interpreter,
 							  true, &arch_state);
 				if (retval)
@@ -839,7 +837,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	 * the exec syscall.
 	 */
 	retval = arch_check_elf(elf_ex,
-				!!interpreter, &loc->interp_elf_ex,
+				!!interpreter, interp_elf_ex,
 				&arch_state);
 	if (retval)
 		goto out_free_dentry;
@@ -1055,7 +1053,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	}
 
 	if (interpreter) {
-		elf_entry = load_elf_interp(&loc->interp_elf_ex,
+		elf_entry = load_elf_interp(interp_elf_ex,
 					    interpreter,
 					    load_bias, interp_elf_phdata);
 		if (!IS_ERR((void *)elf_entry)) {
@@ -1064,7 +1062,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 			 * adjustment
 			 */
 			interp_load_addr = elf_entry;
-			elf_entry += loc->interp_elf_ex.e_entry;
+			elf_entry += interp_elf_ex->e_entry;
 		}
 		if (BAD_ADDR(elf_entry)) {
 			retval = IS_ERR((void *)elf_entry) ?
@@ -1153,7 +1151,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	start_thread(regs, elf_entry, bprm->p);
 	retval = 0;
 out:
-	kfree(loc);
+	kfree(interp_elf_ex);
 out_ret:
 	return retval;
 

[PATCH 2/3] ELF: allocate less for static executable

[Alexey Dobriyan]

PT_INTERP ELF header can be spared if executable is static.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/binfmt_elf.c |   19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -698,17 +698,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long reloc_func_desc __maybe_unused = 0;
 	int executable_stack = EXSTACK_DEFAULT;
 	struct elfhdr *elf_ex = (struct elfhdr *)bprm->buf;
-	struct elfhdr *interp_elf_ex;
+	struct elfhdr *interp_elf_ex = NULL;
 	struct arch_elf_state arch_state = INIT_ARCH_ELF_STATE;
 	struct mm_struct *mm;
 	struct pt_regs *regs;
 
-	interp_elf_ex = kmalloc(sizeof(*interp_elf_ex), GFP_KERNEL);
-	if (!interp_elf_ex) {
-		retval = -ENOMEM;
-		goto out_ret;
-	}
-
 	retval = -ENOEXEC;
 	/* First of all, some simple consistency checks */
 	if (memcmp(elf_ex->e_ident, ELFMAG, SELFMAG) != 0)
@@ -768,6 +762,12 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		 */
 		would_dump(bprm, interpreter);
 
+		interp_elf_ex = kmalloc(sizeof(*interp_elf_ex), GFP_KERNEL);
+		if (!interp_elf_ex) {
+			retval = -ENOMEM;
+			goto out_free_ph;
+		}
+
 		/* Get the exec headers */
 		retval = elf_read(interpreter, interp_elf_ex,
 				  sizeof(*interp_elf_ex), 0);
@@ -1073,6 +1073,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
 
 		allow_write_access(interpreter);
 		fput(interpreter);
+
+		kfree(interp_elf_ex);
 	} else {
 		elf_entry = e_entry;
 		if (BAD_ADDR(elf_entry)) {
@@ -1151,12 +1153,11 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	start_thread(regs, elf_entry, bprm->p);
 	retval = 0;
 out:
-	kfree(interp_elf_ex);
-out_ret:
 	return retval;
 
 	/* error cleanup */
 out_free_dentry:
+	kfree(interp_elf_ex);
 	kfree(interp_elf_phdata);
 	allow_write_access(interpreter);
 	if (interpreter)

[PATCH 3/3] ELF: don't free interpreter's ELF pheaders on common path

[Alexey Dobriyan]

Static executables don't need to free NULL pointer.

It doesn't matter really because static executable is not common
scenario but do it anyway out of pedantry.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/binfmt_elf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1075,6 +1075,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		fput(interpreter);
 
 		kfree(interp_elf_ex);
+		kfree(interp_elf_phdata);
 	} else {
 		elf_entry = e_entry;
 		if (BAD_ADDR(elf_entry)) {
@@ -1083,7 +1084,6 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		}
 	}
 
-	kfree(interp_elf_phdata);
 	kfree(elf_phdata);
 
 	set_binfmt(&elf_format);