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From: Christoph Hellwig <hch@lst.de>
To: Andrew Morton <akpm@linux-foundation.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jeremy Kerr <jk@ozlabs.org>, Arnd Bergmann <arnd@arndb.de>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 7/7] exec: open code copy_string_kernel
Date: Tue, 21 Apr 2020 17:42:04 +0200
Message-ID: <20200421154204.252921-8-hch@lst.de> (raw)
In-Reply-To: <20200421154204.252921-1-hch@lst.de>

Currently copy_string_kernel is just a wrapper around copy_strings that
simplifies the calling conventions and uses set_fs to allow passing a
kernel pointer.  But due to the fact the we only need to handle a single
kernel argument pointer, the logic can be sigificantly simplified while
getting rid of the set_fs.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/exec.c | 43 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 34 insertions(+), 9 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index b2a77d5acede..ea90af1fb236 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -592,17 +592,42 @@ static int copy_strings(int argc, struct user_arg_ptr argv,
  */
 int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
 {
-	int r;
-	mm_segment_t oldfs = get_fs();
-	struct user_arg_ptr argv = {
-		.ptr.native = (const char __user *const  __user *)&arg,
-	};
+	int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
+	unsigned long pos = bprm->p;
+
+	if (len == 0)
+		return -EFAULT;
+	if (!valid_arg_len(bprm, len))
+		return -E2BIG;
+
+	/* We're going to work our way backwards. */
+	arg += len;
+	bprm->p -= len;
+	if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
+		return -E2BIG;
+
+	while (len > 0) {
+		unsigned int bytes_to_copy = min_t(unsigned int, len,
+				min_not_zero(offset_in_page(pos), PAGE_SIZE));
+		struct page *page;
+		char *kaddr;
 
-	set_fs(KERNEL_DS);
-	r = copy_strings(1, argv, bprm);
-	set_fs(oldfs);
+		pos -= bytes_to_copy;
+		arg -= bytes_to_copy;
+		len -= bytes_to_copy;
 
-	return r;
+		page = get_arg_page(bprm, pos, 1);
+		if (!page)
+			return -E2BIG;
+		kaddr = kmap_atomic(page);
+		flush_arg_page(bprm, pos & PAGE_MASK, page);
+		memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
+		flush_kernel_dcache_page(page);
+		kunmap_atomic(kaddr);
+		put_arg_page(page);
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(copy_string_kernel);
 
-- 
2.26.1


      parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-21 15:41 remove set_fs calls from the exec and coredump code v3 Christoph Hellwig
2020-04-21 15:41 ` [PATCH 1/7] powerpc/spufs: simplify spufs core dumping Christoph Hellwig
2020-04-21 18:49   ` Al Viro
2020-04-21 19:01     ` Christoph Hellwig
2020-04-21 19:19       ` Al Viro
2020-04-21 19:25         ` Al Viro
2020-04-21 15:41 ` [PATCH 2/7] signal: factor copy_siginfo_to_external32 from copy_siginfo_to_user32 Christoph Hellwig
2020-04-26  4:47   ` Andrew Morton
2020-04-26  7:40     ` Christoph Hellwig
2020-04-27 22:40       ` Andrew Morton
2020-04-28  7:09         ` Christoph Hellwig
2020-04-28  7:45           ` Christophe Leroy
2020-04-28  7:48             ` Christoph Hellwig
2020-04-28 19:56               ` [PATCH] fixup! " Arnd Bergmann
2020-04-29  6:17                 ` Christophe Leroy
2020-04-29  6:29                   ` Christoph Hellwig
2020-04-29  6:44                 ` Christoph Hellwig
2020-04-29  8:07                   ` Arnd Bergmann
2020-04-29  9:42                     ` Christoph Hellwig
2020-04-29 11:28                       ` Arnd Bergmann
2020-04-29 11:53                 ` Christoph Hellwig
2020-04-29 12:34                   ` Arnd Bergmann
2020-04-21 15:42 ` [PATCH 3/7] binfmt_elf: femove the set_fs in fill_siginfo_note Christoph Hellwig
2020-04-21 15:42 ` [PATCH 4/7] binfmt_elf: remove the set_fs(KERNEL_DS) in elf_core_dump Christoph Hellwig
2020-04-21 15:42 ` [PATCH 5/7] binfmt_elf_fdpic: remove the set_fs(KERNEL_DS) in elf_fdpic_core_dump Christoph Hellwig
2020-04-21 15:42 ` [PATCH 6/7] exec: simplify the copy_strings_kernel calling convention Christoph Hellwig
2020-04-21 15:42 ` Christoph Hellwig [this message]

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