[PATCH AUTOSEL 5.4 1/3] sysv: don't call sb_bread() with pointers_lock held

[PATCH AUTOSEL 5.4 1/3] sysv: don't call sb_bread() with pointers_lock held

[Sasha Levin]

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

[ Upstream commit f123dc86388cb669c3d6322702dc441abc35c31e ]

syzbot is reporting sleep in atomic context in SysV filesystem [1], for
sb_bread() is called with rw_spinlock held.

A "write_lock(&pointers_lock) => read_lock(&pointers_lock) deadlock" bug
and a "sb_bread() with write_lock(&pointers_lock)" bug were introduced by
"Replace BKL for chain locking with sysvfs-private rwlock" in Linux 2.5.12.

Then, "[PATCH] err1-40: sysvfs locking fix" in Linux 2.6.8 fixed the
former bug by moving pointers_lock lock to the callers, but instead
introduced a "sb_bread() with read_lock(&pointers_lock)" bug (which made
this problem easier to hit).

Al Viro suggested that why not to do like get_branch()/get_block()/
find_shared() in Minix filesystem does. And doing like that is almost a
revert of "[PATCH] err1-40: sysvfs locking fix" except that get_branch()
 from with find_shared() is called without write_lock(&pointers_lock).

Reported-by: syzbot <syzbot+69b40dc5fd40f32c199f@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?extid=69b40dc5fd40f32c199f
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://lore.kernel.org/r/0d195f93-a22a-49a2-0020-103534d6f7f6@I-love.SAKURA.ne.jp
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/sysv/itree.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/sysv/itree.c b/fs/sysv/itree.c
index e3d1673b8ec97..ef9bcfeec21ad 100644
--- a/fs/sysv/itree.c
+++ b/fs/sysv/itree.c
@@ -82,9 +82,6 @@ static inline sysv_zone_t *block_end(struct buffer_head *bh)
 	return (sysv_zone_t*)((char*)bh->b_data + bh->b_size);
 }
 
-/*
- * Requires read_lock(&pointers_lock) or write_lock(&pointers_lock)
- */
 static Indirect *get_branch(struct inode *inode,
 			    int depth,
 			    int offsets[],
@@ -104,15 +101,18 @@ static Indirect *get_branch(struct inode *inode,
 		bh = sb_bread(sb, block);
 		if (!bh)
 			goto failure;
+		read_lock(&pointers_lock);
 		if (!verify_chain(chain, p))
 			goto changed;
 		add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
+		read_unlock(&pointers_lock);
 		if (!p->key)
 			goto no_block;
 	}
 	return NULL;
 
 changed:
+	read_unlock(&pointers_lock);
 	brelse(bh);
 	*err = -EAGAIN;
 	goto no_block;
@@ -218,9 +218,7 @@ static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *b
 		goto out;
 
 reread:
-	read_lock(&pointers_lock);
 	partial = get_branch(inode, depth, offsets, chain, &err);
-	read_unlock(&pointers_lock);
 
 	/* Simplest case - block found, no allocation needed */
 	if (!partial) {
@@ -290,9 +288,9 @@ static Indirect *find_shared(struct inode *inode,
 	*top = 0;
 	for (k = depth; k > 1 && !offsets[k-1]; k--)
 		;
+	partial = get_branch(inode, k, offsets, chain, &err);
 
 	write_lock(&pointers_lock);
-	partial = get_branch(inode, k, offsets, chain, &err);
 	if (!partial)
 		partial = chain + k-1;
 	/*
-- 
2.43.0

[PATCH AUTOSEL 5.4 2/3] block: prevent division by zero in blk_rq_stat_sum()

[Sasha Levin]

From: Roman Smirnov <r.smirnov@omp.ru>

[ Upstream commit 93f52fbeaf4b676b21acfe42a5152620e6770d02 ]

The expression dst->nr_samples + src->nr_samples may
have zero value on overflow. It is necessary to add
a check to avoid division by zero.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/20240305134509.23108-1-r.smirnov@omp.ru
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/blk-stat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-stat.c b/block/blk-stat.c
index 940f15d600f8a..af482d8f9f7a4 100644
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -28,7 +28,7 @@ void blk_rq_stat_init(struct blk_rq_stat *stat)
 /* src is a per-cpu stat, mean isn't initialized */
 void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
 {
-	if (!src->nr_samples)
+	if (dst->nr_samples + src->nr_samples <= dst->nr_samples)
 		return;
 
 	dst->min = min(dst->min, src->min);
-- 
2.43.0

[PATCH AUTOSEL 5.4 3/3] nvme: clear caller pointer on identify failure

[Sasha Levin]

From: Keith Busch <kbusch@kernel.org>

[ Upstream commit 7e80eb792bd7377a20f204943ac31c77d859be89 ]

The memory allocated for the identification is freed on failure. Set
it to NULL so the caller doesn't have a pointer to that freed address.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvme/host/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 9144ed14b0741..0676637e1eab6 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1080,8 +1080,10 @@ static int nvme_identify_ctrl(struct nvme_ctrl *dev, struct nvme_id_ctrl **id)
 
 	error = nvme_submit_sync_cmd(dev->admin_q, &c, *id,
 			sizeof(struct nvme_id_ctrl));
-	if (error)
+	if (error) {
 		kfree(*id);
+		*id = NULL;
+	}
 	return error;
 }
 
@@ -1193,6 +1195,7 @@ static int nvme_identify_ns(struct nvme_ctrl *ctrl,
 	if (error) {
 		dev_warn(ctrl->device, "Identify namespace failed (%d)\n", error);
 		kfree(*id);
+		*id = NULL;
 	}
 
 	return error;
-- 
2.43.0