* [PATCH] locks: fix TOCTOU race when granting write lease
@ 2022-08-14 15:23 Amir Goldstein
2022-08-14 17:57 ` Al Viro
2022-08-15 11:21 ` Jeff Layton
0 siblings, 2 replies; 6+ messages in thread
From: Amir Goldstein @ 2022-08-14 15:23 UTC (permalink / raw)
To: Jeff Layton; +Cc: Chuck Lever, Al Viro, linux-fsdevel
Thread A trying to acquire a write lease checks the value of i_readcount
and i_writecount in check_conflicting_open() to verify that its own fd
is the only fd referencing the file.
Thread B trying to open the file for read will call break_lease() in
do_dentry_open() before incrementing i_readcount, which leaves a small
window where thread A can acquire the write lease and then thread B
completes the open of the file for read without breaking the write lease
that was acquired by thread A.
Fix this race by incrementing i_readcount before checking for existing
leases, same as the case with i_writecount.
Use a helper put_file_access() to decrement i_readcount or i_writecount
in do_dentry_open() and __fput().
Fixes: 387e3746d01c ("locks: eliminate false positive conflicts for write lease")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
Hi Jeff,
This fixes a race I found during code audit - I do not have a reproducer
for it.
I ran the fstests I found for locks and leases:
generic/131 generic/478 generic/504 generic/571
and the LTP fcntl tests.
Encountered this warning with generic/131, but I also see it on
current master:
=============================
WARNING: suspicious RCU usage
5.19.0-xfstests-14277-gbd6ab3ef4e93 #966 Not tainted
-----------------------------
include/net/sock.h:592 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
5 locks held by locktest/3996:
#0: ffff88800be1d7a0 (&sb->s_type->i_mutex_key#8){+.+.}-{3:3}, at: __sock_release+0x25/0x97
#1: ffff88800909ce00 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_close+0x14/0x60
#2: ffff888006847cc8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: inet_unhash+0x3a/0xcf
#3: ffffffff82a8ac18 (reuseport_lock){+...}-{2:2}, at: reuseport_detach_sock+0x17/0xb8
#4: ffff88800909d0b0 (clock-AF_INET){++..}-{2:2}, at: bpf_sk_reuseport_detach+0x1b/0x85
stack backtrace:
CPU: 1 PID: 3996 Comm: locktest Not tainted 5.19.0-xfstests-14277-gbd6ab3ef4e93 #966
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x45/0x5d
bpf_sk_reuseport_detach+0x5c/0x85
reuseport_detach_sock+0x65/0xb8
inet_unhash+0x55/0xcf
tcp_set_state+0xb3/0x10d
? mark_lock.part.0+0x30/0x101
__tcp_close+0x26/0x32d
tcp_close+0x20/0x60
inet_release+0x50/0x64
__sock_release+0x32/0x97
sock_close+0x14/0x1b
__fput+0x118/0x1eb
Let me know what you think.
Thanks,
Amir.
fs/file_table.c | 7 +------
fs/open.c | 11 ++++-------
include/linux/fs.h | 10 ++++++++++
3 files changed, 15 insertions(+), 13 deletions(-)
diff --git a/fs/file_table.c b/fs/file_table.c
index 99c6796c9f28..dd88701e54a9 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -324,12 +324,7 @@ static void __fput(struct file *file)
}
fops_put(file->f_op);
put_pid(file->f_owner.pid);
- if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
- i_readcount_dec(inode);
- if (mode & FMODE_WRITER) {
- put_write_access(inode);
- __mnt_drop_write(mnt);
- }
+ put_file_access(file);
dput(dentry);
if (unlikely(mode & FMODE_NEED_UNMOUNT))
dissolve_on_fput(mnt);
diff --git a/fs/open.c b/fs/open.c
index 8a813fa5ca56..a98572585815 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -840,7 +840,9 @@ static int do_dentry_open(struct file *f,
return 0;
}
- if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
+ if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
+ i_readcount_inc(inode);
+ } else if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
error = get_write_access(inode);
if (unlikely(error))
goto cleanup_file;
@@ -880,8 +882,6 @@ static int do_dentry_open(struct file *f,
goto cleanup_all;
}
f->f_mode |= FMODE_OPENED;
- if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
- i_readcount_inc(inode);
if ((f->f_mode & FMODE_READ) &&
likely(f->f_op->read || f->f_op->read_iter))
f->f_mode |= FMODE_CAN_READ;
@@ -935,10 +935,7 @@ static int do_dentry_open(struct file *f,
if (WARN_ON_ONCE(error > 0))
error = -EINVAL;
fops_put(f->f_op);
- if (f->f_mode & FMODE_WRITER) {
- put_write_access(inode);
- __mnt_drop_write(f->f_path.mnt);
- }
+ put_file_access(f);
cleanup_file:
path_put(&f->f_path);
f->f_path.mnt = NULL;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9eced4cc286e..8bc04852c3da 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3000,6 +3000,16 @@ static inline void i_readcount_inc(struct inode *inode)
return;
}
#endif
+static inline void put_file_access(struct file *file)
+{
+ if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
+ i_readcount_dec(file->f_inode);
+ } else if (file->f_mode & FMODE_WRITER) {
+ put_write_access(file->f_inode);
+ __mnt_drop_write(file->f_path.mnt);
+ }
+}
+
extern int do_pipe_flags(int *, int);
extern ssize_t kernel_read(struct file *, void *, size_t, loff_t *);
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] locks: fix TOCTOU race when granting write lease
2022-08-14 15:23 [PATCH] locks: fix TOCTOU race when granting write lease Amir Goldstein
@ 2022-08-14 17:57 ` Al Viro
2022-08-15 7:18 ` Amir Goldstein
2022-08-15 11:21 ` Jeff Layton
1 sibling, 1 reply; 6+ messages in thread
From: Al Viro @ 2022-08-14 17:57 UTC (permalink / raw)
To: Amir Goldstein; +Cc: Jeff Layton, Chuck Lever, linux-fsdevel
On Sun, Aug 14, 2022 at 06:23:22PM +0300, Amir Goldstein wrote:
> Thread A trying to acquire a write lease checks the value of i_readcount
> and i_writecount in check_conflicting_open() to verify that its own fd
> is the only fd referencing the file.
>
> Thread B trying to open the file for read will call break_lease() in
> do_dentry_open() before incrementing i_readcount, which leaves a small
> window where thread A can acquire the write lease and then thread B
> completes the open of the file for read without breaking the write lease
> that was acquired by thread A.
>
> Fix this race by incrementing i_readcount before checking for existing
> leases, same as the case with i_writecount.
>
> Use a helper put_file_access() to decrement i_readcount or i_writecount
> in do_dentry_open() and __fput().
>
> Fixes: 387e3746d01c ("locks: eliminate false positive conflicts for write lease")
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Looks sane; I'd probably collapsed cleanup_file and cleanup_all while we are
at it, but then I can do that in a followup as well.
> +static inline void put_file_access(struct file *file)
> +{
> + if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> + i_readcount_dec(file->f_inode);
> + } else if (file->f_mode & FMODE_WRITER) {
> + put_write_access(file->f_inode);
> + __mnt_drop_write(file->f_path.mnt);
> + }
> +}
What's the point of having it in linux/fs.h instead of internal.h?
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] locks: fix TOCTOU race when granting write lease
2022-08-14 17:57 ` Al Viro
@ 2022-08-15 7:18 ` Amir Goldstein
2022-08-16 3:18 ` Al Viro
0 siblings, 1 reply; 6+ messages in thread
From: Amir Goldstein @ 2022-08-15 7:18 UTC (permalink / raw)
To: Al Viro; +Cc: Jeff Layton, Chuck Lever, linux-fsdevel
On Sun, Aug 14, 2022 at 8:57 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Sun, Aug 14, 2022 at 06:23:22PM +0300, Amir Goldstein wrote:
> > Thread A trying to acquire a write lease checks the value of i_readcount
> > and i_writecount in check_conflicting_open() to verify that its own fd
> > is the only fd referencing the file.
> >
> > Thread B trying to open the file for read will call break_lease() in
> > do_dentry_open() before incrementing i_readcount, which leaves a small
> > window where thread A can acquire the write lease and then thread B
> > completes the open of the file for read without breaking the write lease
> > that was acquired by thread A.
> >
> > Fix this race by incrementing i_readcount before checking for existing
> > leases, same as the case with i_writecount.
> >
> > Use a helper put_file_access() to decrement i_readcount or i_writecount
> > in do_dentry_open() and __fput().
> >
> > Fixes: 387e3746d01c ("locks: eliminate false positive conflicts for write lease")
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>
> Looks sane; I'd probably collapsed cleanup_file and cleanup_all while we are
> at it, but then I can do that in a followup as well.
>
Not sure how you envision that cleanup, so I'll let you do it.
> > +static inline void put_file_access(struct file *file)
> > +{
> > + if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> > + i_readcount_dec(file->f_inode);
> > + } else if (file->f_mode & FMODE_WRITER) {
> > + put_write_access(file->f_inode);
> > + __mnt_drop_write(file->f_path.mnt);
> > + }
> > +}
>
> What's the point of having it in linux/fs.h instead of internal.h?
No reason. Overlooked.
Do you need me to re-send or will you move it to internal.h yourself?
Thanks,
Amir.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] locks: fix TOCTOU race when granting write lease
2022-08-15 7:18 ` Amir Goldstein
@ 2022-08-16 3:18 ` Al Viro
0 siblings, 0 replies; 6+ messages in thread
From: Al Viro @ 2022-08-16 3:18 UTC (permalink / raw)
To: Amir Goldstein; +Cc: Jeff Layton, Chuck Lever, linux-fsdevel
On Mon, Aug 15, 2022 at 10:18:21AM +0300, Amir Goldstein wrote:
> > > +static inline void put_file_access(struct file *file)
> > > +{
> > > + if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> > > + i_readcount_dec(file->f_inode);
> > > + } else if (file->f_mode & FMODE_WRITER) {
> > > + put_write_access(file->f_inode);
> > > + __mnt_drop_write(file->f_path.mnt);
> > > + }
> > > +}
> >
> > What's the point of having it in linux/fs.h instead of internal.h?
>
> No reason. Overlooked.
> Do you need me to re-send or will you move it to internal.h yourself?
Resend, please...
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] locks: fix TOCTOU race when granting write lease
2022-08-14 15:23 [PATCH] locks: fix TOCTOU race when granting write lease Amir Goldstein
2022-08-14 17:57 ` Al Viro
@ 2022-08-15 11:21 ` Jeff Layton
2022-08-16 14:03 ` Amir Goldstein
1 sibling, 1 reply; 6+ messages in thread
From: Jeff Layton @ 2022-08-15 11:21 UTC (permalink / raw)
To: Amir Goldstein; +Cc: Chuck Lever, Al Viro, linux-fsdevel
On Sun, 2022-08-14 at 18:23 +0300, Amir Goldstein wrote:
> Thread A trying to acquire a write lease checks the value of i_readcount
> and i_writecount in check_conflicting_open() to verify that its own fd
> is the only fd referencing the file.
>
> Thread B trying to open the file for read will call break_lease() in
> do_dentry_open() before incrementing i_readcount, which leaves a small
> window where thread A can acquire the write lease and then thread B
> completes the open of the file for read without breaking the write lease
> that was acquired by thread A.
>
> Fix this race by incrementing i_readcount before checking for existing
> leases, same as the case with i_writecount.
>
Nice catch.
> Use a helper put_file_access() to decrement i_readcount or i_writecount
> in do_dentry_open() and __fput().
>
> Fixes: 387e3746d01c ("locks: eliminate false positive conflicts for write lease")
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>
> Hi Jeff,
>
> This fixes a race I found during code audit - I do not have a reproducer
> for it.
>
> I ran the fstests I found for locks and leases:
> generic/131 generic/478 generic/504 generic/571
> and the LTP fcntl tests.
>
> Encountered this warning with generic/131, but I also see it on
> current master:
>
> =============================
> WARNING: suspicious RCU usage
> 5.19.0-xfstests-14277-gbd6ab3ef4e93 #966 Not tainted
> -----------------------------
> include/net/sock.h:592 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 1
> 5 locks held by locktest/3996:
> #0: ffff88800be1d7a0 (&sb->s_type->i_mutex_key#8){+.+.}-{3:3}, at: __sock_release+0x25/0x97
> #1: ffff88800909ce00 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_close+0x14/0x60
> #2: ffff888006847cc8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: inet_unhash+0x3a/0xcf
> #3: ffffffff82a8ac18 (reuseport_lock){+...}-{2:2}, at: reuseport_detach_sock+0x17/0xb8
> #4: ffff88800909d0b0 (clock-AF_INET){++..}-{2:2}, at: bpf_sk_reuseport_detach+0x1b/0x85
>
> stack backtrace:
> CPU: 1 PID: 3996 Comm: locktest Not tainted 5.19.0-xfstests-14277-gbd6ab3ef4e93 #966
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
> Call Trace:
> <TASK>
> dump_stack_lvl+0x45/0x5d
> bpf_sk_reuseport_detach+0x5c/0x85
> reuseport_detach_sock+0x65/0xb8
> inet_unhash+0x55/0xcf
> tcp_set_state+0xb3/0x10d
> ? mark_lock.part.0+0x30/0x101
> __tcp_close+0x26/0x32d
> tcp_close+0x20/0x60
> inet_release+0x50/0x64
> __sock_release+0x32/0x97
> sock_close+0x14/0x1b
> __fput+0x118/0x1eb
>
>
> Let me know what you think.
>
> Thanks,
> Amir.
>
> fs/file_table.c | 7 +------
> fs/open.c | 11 ++++-------
> include/linux/fs.h | 10 ++++++++++
> 3 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 99c6796c9f28..dd88701e54a9 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -324,12 +324,7 @@ static void __fput(struct file *file)
> }
> fops_put(file->f_op);
> put_pid(file->f_owner.pid);
> - if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
> - i_readcount_dec(inode);
> - if (mode & FMODE_WRITER) {
> - put_write_access(inode);
> - __mnt_drop_write(mnt);
> - }
> + put_file_access(file);
> dput(dentry);
> if (unlikely(mode & FMODE_NEED_UNMOUNT))
> dissolve_on_fput(mnt);
> diff --git a/fs/open.c b/fs/open.c
> index 8a813fa5ca56..a98572585815 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -840,7 +840,9 @@ static int do_dentry_open(struct file *f,
> return 0;
> }
>
> - if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
> + if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> + i_readcount_inc(inode);
> + } else if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
> error = get_write_access(inode);
> if (unlikely(error))
> goto cleanup_file;
> @@ -880,8 +882,6 @@ static int do_dentry_open(struct file *f,
> goto cleanup_all;
> }
> f->f_mode |= FMODE_OPENED;
> - if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
> - i_readcount_inc(inode);
> if ((f->f_mode & FMODE_READ) &&
> likely(f->f_op->read || f->f_op->read_iter))
> f->f_mode |= FMODE_CAN_READ;
> @@ -935,10 +935,7 @@ static int do_dentry_open(struct file *f,
> if (WARN_ON_ONCE(error > 0))
> error = -EINVAL;
> fops_put(f->f_op);
> - if (f->f_mode & FMODE_WRITER) {
> - put_write_access(inode);
> - __mnt_drop_write(f->f_path.mnt);
> - }
> + put_file_access(f);
> cleanup_file:
> path_put(&f->f_path);
> f->f_path.mnt = NULL;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9eced4cc286e..8bc04852c3da 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3000,6 +3000,16 @@ static inline void i_readcount_inc(struct inode *inode)
> return;
> }
> #endif
> +static inline void put_file_access(struct file *file)
> +{
> + if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> + i_readcount_dec(file->f_inode);
> + } else if (file->f_mode & FMODE_WRITER) {
> + put_write_access(file->f_inode);
> + __mnt_drop_write(file->f_path.mnt);
> + }
> +}
> +
> extern int do_pipe_flags(int *, int);
>
> extern ssize_t kernel_read(struct file *, void *, size_t, loff_t *);
Looks good to me. I like the new helper.
In addition to Al's comment about which header this should go in, it
might also be good to put a kerneldoc comment over it.
Al, did you want to take this via your tree or do you want me to take it
via the filelocks tree?
Thanks,
--
Jeff Layton <jlayton@kernel.org>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] locks: fix TOCTOU race when granting write lease
2022-08-15 11:21 ` Jeff Layton
@ 2022-08-16 14:03 ` Amir Goldstein
0 siblings, 0 replies; 6+ messages in thread
From: Amir Goldstein @ 2022-08-16 14:03 UTC (permalink / raw)
To: Jeff Layton; +Cc: Chuck Lever, Al Viro, linux-fsdevel
On Mon, Aug 15, 2022 at 2:21 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Sun, 2022-08-14 at 18:23 +0300, Amir Goldstein wrote:
> > Thread A trying to acquire a write lease checks the value of i_readcount
> > and i_writecount in check_conflicting_open() to verify that its own fd
> > is the only fd referencing the file.
> >
> > Thread B trying to open the file for read will call break_lease() in
> > do_dentry_open() before incrementing i_readcount, which leaves a small
> > window where thread A can acquire the write lease and then thread B
> > completes the open of the file for read without breaking the write lease
> > that was acquired by thread A.
> >
> > Fix this race by incrementing i_readcount before checking for existing
> > leases, same as the case with i_writecount.
> >
>
> Nice catch.
>
> > Use a helper put_file_access() to decrement i_readcount or i_writecount
> > in do_dentry_open() and __fput().
> >
> > Fixes: 387e3746d01c ("locks: eliminate false positive conflicts for write lease")
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > ---
> >
> > Hi Jeff,
> >
> > This fixes a race I found during code audit - I do not have a reproducer
> > for it.
> >
> > I ran the fstests I found for locks and leases:
> > generic/131 generic/478 generic/504 generic/571
> > and the LTP fcntl tests.
> >
> > Encountered this warning with generic/131, but I also see it on
> > current master:
> >
> > =============================
> > WARNING: suspicious RCU usage
> > 5.19.0-xfstests-14277-gbd6ab3ef4e93 #966 Not tainted
> > -----------------------------
> > include/net/sock.h:592 suspicious rcu_dereference_check() usage!
> >
> > other info that might help us debug this:
> >
> >
> > rcu_scheduler_active = 2, debug_locks = 1
> > 5 locks held by locktest/3996:
> > #0: ffff88800be1d7a0 (&sb->s_type->i_mutex_key#8){+.+.}-{3:3}, at: __sock_release+0x25/0x97
> > #1: ffff88800909ce00 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_close+0x14/0x60
> > #2: ffff888006847cc8 (&h->lhash2[i].lock){+.+.}-{2:2}, at: inet_unhash+0x3a/0xcf
> > #3: ffffffff82a8ac18 (reuseport_lock){+...}-{2:2}, at: reuseport_detach_sock+0x17/0xb8
> > #4: ffff88800909d0b0 (clock-AF_INET){++..}-{2:2}, at: bpf_sk_reuseport_detach+0x1b/0x85
> >
> > stack backtrace:
> > CPU: 1 PID: 3996 Comm: locktest Not tainted 5.19.0-xfstests-14277-gbd6ab3ef4e93 #966
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0x45/0x5d
> > bpf_sk_reuseport_detach+0x5c/0x85
> > reuseport_detach_sock+0x65/0xb8
> > inet_unhash+0x55/0xcf
> > tcp_set_state+0xb3/0x10d
> > ? mark_lock.part.0+0x30/0x101
> > __tcp_close+0x26/0x32d
> > tcp_close+0x20/0x60
> > inet_release+0x50/0x64
> > __sock_release+0x32/0x97
> > sock_close+0x14/0x1b
> > __fput+0x118/0x1eb
> >
> >
> > Let me know what you think.
> >
> > Thanks,
> > Amir.
> >
> > fs/file_table.c | 7 +------
> > fs/open.c | 11 ++++-------
> > include/linux/fs.h | 10 ++++++++++
> > 3 files changed, 15 insertions(+), 13 deletions(-)
> >
> > diff --git a/fs/file_table.c b/fs/file_table.c
> > index 99c6796c9f28..dd88701e54a9 100644
> > --- a/fs/file_table.c
> > +++ b/fs/file_table.c
> > @@ -324,12 +324,7 @@ static void __fput(struct file *file)
> > }
> > fops_put(file->f_op);
> > put_pid(file->f_owner.pid);
> > - if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
> > - i_readcount_dec(inode);
> > - if (mode & FMODE_WRITER) {
> > - put_write_access(inode);
> > - __mnt_drop_write(mnt);
> > - }
> > + put_file_access(file);
> > dput(dentry);
> > if (unlikely(mode & FMODE_NEED_UNMOUNT))
> > dissolve_on_fput(mnt);
> > diff --git a/fs/open.c b/fs/open.c
> > index 8a813fa5ca56..a98572585815 100644
> > --- a/fs/open.c
> > +++ b/fs/open.c
> > @@ -840,7 +840,9 @@ static int do_dentry_open(struct file *f,
> > return 0;
> > }
> >
> > - if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
> > + if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> > + i_readcount_inc(inode);
> > + } else if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
> > error = get_write_access(inode);
> > if (unlikely(error))
> > goto cleanup_file;
> > @@ -880,8 +882,6 @@ static int do_dentry_open(struct file *f,
> > goto cleanup_all;
> > }
> > f->f_mode |= FMODE_OPENED;
> > - if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
> > - i_readcount_inc(inode);
> > if ((f->f_mode & FMODE_READ) &&
> > likely(f->f_op->read || f->f_op->read_iter))
> > f->f_mode |= FMODE_CAN_READ;
> > @@ -935,10 +935,7 @@ static int do_dentry_open(struct file *f,
> > if (WARN_ON_ONCE(error > 0))
> > error = -EINVAL;
> > fops_put(f->f_op);
> > - if (f->f_mode & FMODE_WRITER) {
> > - put_write_access(inode);
> > - __mnt_drop_write(f->f_path.mnt);
> > - }
> > + put_file_access(f);
> > cleanup_file:
> > path_put(&f->f_path);
> > f->f_path.mnt = NULL;
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 9eced4cc286e..8bc04852c3da 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -3000,6 +3000,16 @@ static inline void i_readcount_inc(struct inode *inode)
> > return;
> > }
> > #endif
> > +static inline void put_file_access(struct file *file)
> > +{
> > + if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
> > + i_readcount_dec(file->f_inode);
> > + } else if (file->f_mode & FMODE_WRITER) {
> > + put_write_access(file->f_inode);
> > + __mnt_drop_write(file->f_path.mnt);
> > + }
> > +}
> > +
> > extern int do_pipe_flags(int *, int);
> >
> > extern ssize_t kernel_read(struct file *, void *, size_t, loff_t *);
>
> Looks good to me. I like the new helper.
>
> In addition to Al's comment about which header this should go in, it
> might also be good to put a kerneldoc comment over it.
>
I'm sorry, I couldn't come up with a good description of
this arbitrary helper and I don't think this is so important
for an internal helper like this one.
For now, I will post without the kerneldoc.
If you disagree, please provide a description.
Thanks,
Amir.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-08-16 14:05 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-08-14 15:23 [PATCH] locks: fix TOCTOU race when granting write lease Amir Goldstein
2022-08-14 17:57 ` Al Viro
2022-08-15 7:18 ` Amir Goldstein
2022-08-16 3:18 ` Al Viro
2022-08-15 11:21 ` Jeff Layton
2022-08-16 14:03 ` Amir Goldstein
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