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

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Date:   Tue,  5 May 2020 12:12:56 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jeremy Kerr <jk@...abs.org>, Arnd Bergmann <arnd@...db.de>,
        Oleg Nesterov <oleg@...hat.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>, x86@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 7/7] 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 | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 240f666635437..d9501a86cec97 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;
@@ -1589,31 +1588,31 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	/* alloc memory for large data structures: too large to be on stack */
 	elf = kmalloc(sizeof(*elf), GFP_KERNEL);
 	if (!elf)
-		goto cleanup;
+		goto end_coredump;
 	prstatus = kzalloc(sizeof(*prstatus), GFP_KERNEL);
 	if (!prstatus)
-		goto cleanup;
+		goto end_coredump;
 	psinfo = kmalloc(sizeof(*psinfo), GFP_KERNEL);
 	if (!psinfo)
-		goto cleanup;
+		goto end_coredump;
 	notes = kmalloc_array(NUM_NOTES, sizeof(struct memelfnote),
 			      GFP_KERNEL);
 	if (!notes)
-		goto cleanup;
+		goto end_coredump;
 	fpu = kmalloc(sizeof(*fpu), GFP_KERNEL);
 	if (!fpu)
-		goto cleanup;
+		goto end_coredump;
 #ifdef ELF_CORE_COPY_XFPREGS
 	xfpu = kmalloc(sizeof(*xfpu), GFP_KERNEL);
 	if (!xfpu)
-		goto cleanup;
+		goto end_coredump;
 #endif
 
 	for (ct = current->mm->core_state->dumper.next;
 					ct; ct = ct->next) {
 		tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
 		if (!tmp)
-			goto cleanup;
+			goto end_coredump;
 
 		tmp->thread = ct->task;
 		list_add(&tmp->list, &thread_list);
@@ -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 */
 
@@ -1788,9 +1784,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	}
 
 end_coredump:
-	set_fs(fs);
-
-cleanup:
 	while (!list_empty(&thread_list)) {
 		struct list_head *tmp = thread_list.next;
 		list_del(tmp);
-- 
2.26.2