From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
Jan Stancek <jstancek@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 4.19 23/33] fat: work around race with userspace's read via blockdev while mounting
Date: Sun, 29 Sep 2019 13:34:11 -0400 [thread overview]
Message-ID: <20190929173424.9361-23-sashal@kernel.org> (raw)
In-Reply-To: <20190929173424.9361-1-sashal@kernel.org>
From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
[ Upstream commit 07bfa4415ab607e459b69bd86aa7e7602ce10b4f ]
If userspace reads the buffer via blockdev while mounting,
sb_getblk()+modify can race with buffer read via blockdev.
For example,
FS userspace
bh = sb_getblk()
modify bh->b_data
read
ll_rw_block(bh)
fill bh->b_data by on-disk data
/* lost modified data by FS */
set_buffer_uptodate(bh)
set_buffer_uptodate(bh)
Userspace should not use the blockdev while mounting though, the udev
seems to be already doing this. Although I think the udev should try to
avoid this, workaround the race by small overhead.
Link: http://lkml.kernel.org/r/87pnk7l3sw.fsf_-_@mail.parknet.co.jp
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reported-by: Jan Stancek <jstancek@redhat.com>
Tested-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/fat/dir.c | 13 +++++++++++--
fs/fat/fatent.c | 3 +++
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 7f5f3699fc6c0..de60c05c0ca1d 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -1097,8 +1097,11 @@ static int fat_zeroed_cluster(struct inode *dir, sector_t blknr, int nr_used,
err = -ENOMEM;
goto error;
}
+ /* Avoid race with userspace read via bdev */
+ lock_buffer(bhs[n]);
memset(bhs[n]->b_data, 0, sb->s_blocksize);
set_buffer_uptodate(bhs[n]);
+ unlock_buffer(bhs[n]);
mark_buffer_dirty_inode(bhs[n], dir);
n++;
@@ -1155,6 +1158,8 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts)
fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
de = (struct msdos_dir_entry *)bhs[0]->b_data;
+ /* Avoid race with userspace read via bdev */
+ lock_buffer(bhs[0]);
/* filling the new directory slots ("." and ".." entries) */
memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
@@ -1177,6 +1182,7 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts)
de[0].size = de[1].size = 0;
memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
set_buffer_uptodate(bhs[0]);
+ unlock_buffer(bhs[0]);
mark_buffer_dirty_inode(bhs[0], dir);
err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
@@ -1234,11 +1240,14 @@ static int fat_add_new_entries(struct inode *dir, void *slots, int nr_slots,
/* fill the directory entry */
copy = min(size, sb->s_blocksize);
+ /* Avoid race with userspace read via bdev */
+ lock_buffer(bhs[n]);
memcpy(bhs[n]->b_data, slots, copy);
- slots += copy;
- size -= copy;
set_buffer_uptodate(bhs[n]);
+ unlock_buffer(bhs[n]);
mark_buffer_dirty_inode(bhs[n], dir);
+ slots += copy;
+ size -= copy;
if (!size)
break;
n++;
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index f58c0cacc531d..4c6c635bc8aaa 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -390,8 +390,11 @@ static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
err = -ENOMEM;
goto error;
}
+ /* Avoid race with userspace read via bdev */
+ lock_buffer(c_bh);
memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
set_buffer_uptodate(c_bh);
+ unlock_buffer(c_bh);
mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
if (sb->s_flags & SB_SYNCHRONOUS)
err = sync_dirty_buffer(c_bh);
--
2.20.1
next prev parent reply other threads:[~2019-09-29 17:39 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-29 17:33 [PATCH AUTOSEL 4.19 01/33] MIPS: Ingenic: Disable broken BTB lookup optimization Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 02/33] clk: jz4740: Add TCU clock Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 03/33] MIPS: tlbex: Explicitly cast _PAGE_NO_EXEC to a boolean Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 04/33] i2c-cht-wc: Fix lockdep warning Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 05/33] mfd: intel-lpss: Remove D3cold delay Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 06/33] PCI: tegra: Fix OF node reference leak Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 07/33] HID: wacom: Fix several minor compiler warnings Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 08/33] livepatch: Nullify obj->mod in klp_module_coming()'s error path Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 09/33] ARM: 8898/1: mm: Don't treat faults reported from cache maintenance as writes Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 10/33] soundwire: intel: fix channel number reported by hardware Sasha Levin
2019-09-29 17:33 ` [PATCH AUTOSEL 4.19 11/33] ARM: 8875/1: Kconfig: default to AEABI w/ Clang Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 12/33] MIPS: lantiq: update the clock alias' for the mainline PCIe PHY driver Sasha Levin
2019-09-29 17:40 ` Martin Blumenstingl
2019-10-05 23:01 ` Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 13/33] firmware: bcm47xx_nvram: Correct size_t printf format Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 14/33] rtc: snvs: fix possible race condition Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 15/33] rtc: pcf85363/pcf85263: fix regmap error in set_time Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 16/33] HID: apple: Fix stuck function keys when using FN Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 17/33] PCI: rockchip: Propagate errors for optional regulators Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 18/33] PCI: histb: " Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 19/33] PCI: imx6: " Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 20/33] PCI: exynos: Propagate errors for optional PHYs Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 21/33] security: smack: Fix possible null-pointer dereferences in smack_socket_sock_rcv_skb() Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 22/33] ARM: 8903/1: ensure that usable memory in bank 0 starts from a PMD-aligned address Sasha Levin
2019-09-29 17:34 ` Sasha Levin [this message]
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 24/33] pktcdvd: remove warning on attempting to register non-passthrough dev Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 25/33] hypfs: Fix error number left in struct pointer member Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 26/33] crypto: hisilicon - Fix double free in sec_free_hw_sgl() Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 27/33] kbuild: clean compressed initramfs image Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 28/33] ocfs2: wait for recovering done after direct unlock request Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 29/33] kmemleak: increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE default to 16K Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 30/33] arm64: consider stack randomization for mmap base only when necessary Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 31/33] mips: properly account for stack randomization and stack guard gap Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 32/33] arm: " Sasha Levin
2019-09-29 17:34 ` [PATCH AUTOSEL 4.19 33/33] arm: use STACK_TOP when computing mmap base address Sasha Levin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190929173424.9361-23-sashal@kernel.org \
--to=sashal@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=hirofumi@mail.parknet.co.jp \
--cc=jstancek@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=stable@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).