linux-kernel - [PATCH 5/7] binfmt_elf_fdpic: remove the set_fs(KERNEL_DS) in elf_fdpic_core

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Date:   Tue, 21 Apr 2020 17:42:02 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     Jeremy Kerr <jk@...abs.org>, Arnd Bergmann <arnd@...db.de>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 5/7] binfmt_elf_fdpic: remove the set_fs(KERNEL_DS) in elf_fdpic_core_dump

There is no logic in elf_fdpic_core_dump itself, or in the various arch
helpers called from it which use uaccess routines on kernel pointers
except for the file writes thate are nicely encapsulated by using
__kernel_write in dump_emit.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 fs/binfmt_elf_fdpic.c | 31 ++++++++++++-------------------
 1 file changed, 12 insertions(+), 19 deletions(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 240f66663543..c62c17a5c34a 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1549,7 +1549,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 {
 #define	NUM_NOTES	6
 	int has_dumped = 0;
-	mm_segment_t fs;
 	int segs;
 	int i;
 	struct vm_area_struct *vma;
@@ -1678,9 +1677,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 			  "LINUX", ELF_CORE_XFPREG_TYPE, sizeof(*xfpu), xfpu);
 #endif
 
-	fs = get_fs();
-	set_fs(KERNEL_DS);
-
 	offset += sizeof(*elf);				/* Elf header */
 	offset += segs * sizeof(struct elf_phdr);	/* Program headers */
 
@@ -1695,7 +1691,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 
 		phdr4note = kmalloc(sizeof(*phdr4note), GFP_KERNEL);
 		if (!phdr4note)
-			goto end_coredump;
+			goto cleanup;
 
 		fill_elf_note_phdr(phdr4note, sz, offset);
 		offset += sz;
@@ -1711,17 +1707,17 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	if (e_phnum == PN_XNUM) {
 		shdr4extnum = kmalloc(sizeof(*shdr4extnum), GFP_KERNEL);
 		if (!shdr4extnum)
-			goto end_coredump;
+			goto cleanup;
 		fill_extnum_info(elf, shdr4extnum, e_shoff, segs);
 	}
 
 	offset = dataoff;
 
 	if (!dump_emit(cprm, elf, sizeof(*elf)))
-		goto end_coredump;
+		goto cleanup;
 
 	if (!dump_emit(cprm, phdr4note, sizeof(*phdr4note)))
-		goto end_coredump;
+		goto cleanup;
 
 	/* write program headers for segments dump */
 	for (vma = current->mm->mmap; vma; vma = vma->vm_next) {
@@ -1745,16 +1741,16 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 		phdr.p_align = ELF_EXEC_PAGESIZE;
 
 		if (!dump_emit(cprm, &phdr, sizeof(phdr)))
-			goto end_coredump;
+			goto cleanup;
 	}
 
 	if (!elf_core_write_extra_phdrs(cprm, offset))
-		goto end_coredump;
+		goto cleanup;
 
  	/* write out the notes section */
 	for (i = 0; i < numnote; i++)
 		if (!writenote(notes + i, cprm))
-			goto end_coredump;
+			goto cleanup;
 
 	/* write out the thread status notes section */
 	list_for_each(t, &thread_list) {
@@ -1763,21 +1759,21 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 
 		for (i = 0; i < tmp->num_notes; i++)
 			if (!writenote(&tmp->notes[i], cprm))
-				goto end_coredump;
+				goto cleanup;
 	}
 
 	if (!dump_skip(cprm, dataoff - cprm->pos))
-		goto end_coredump;
+		goto cleanup;
 
 	if (!elf_fdpic_dump_segments(cprm))
-		goto end_coredump;
+		goto cleanup;
 
 	if (!elf_core_write_extra_data(cprm))
-		goto end_coredump;
+		goto cleanup;
 
 	if (e_phnum == PN_XNUM) {
 		if (!dump_emit(cprm, shdr4extnum, sizeof(*shdr4extnum)))
-			goto end_coredump;
+			goto cleanup;
 	}
 
 	if (cprm->file->f_pos != offset) {
@@ -1787,9 +1783,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 		       cprm->file->f_pos, offset);
 	}
 
-end_coredump:
-	set_fs(fs);
-
 cleanup:
 	while (!list_empty(&thread_list)) {
 		struct list_head *tmp = thread_list.next;
-- 
2.26.1