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vfs: partially revert "don't allow writes to swap files"

PATCH In review Darrick J. Wong 1 participant 2 messages Mar 3, 2020 – Mar 4, 2020

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Memory management VFS MM core Memory mapping +1 more subsystems
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Darrick J. Wong

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#0 lore raw

PATCH 1/1 vfs: partially revert "don't allow writes to swap files"

From: Darrick J. Wong <[email protected]>

In commit dc617f29dbe5 we tried to prevent userspace programs from writing to active swap devices. However, it turns out that userspace hibernation requires the ability to write the hibernation image to a swap device, so revert the write path checks.

Fixes dc617f29dbe5 ("vfs: don't allow writes to swap files")
Reported-by Domenico Andreoli <[email protected]>
Reported-by Marian Klein <[email protected]>
Signed-off-by Darrick J. Wong <[email protected]>
---
 fs/block_dev.c |    3 ---
 mm/filemap.c   |    3 ---
 mm/memory.c    |    4 ----
 mm/mmap.c      |    8 ++------
 4 files changed, 2 insertions(+), 16 deletions(-)
fs/block_dev.c +0 -3
index 69bf2fb6f7cd..08b088dac1f0 100644
@@ -2001,9 +2001,6 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (bdev_read_only(I_BDEV(bd_inode)))
 		return -EPERM;
 
-	if (IS_SWAPFILE(bd_inode))
-		return -ETXTBSY;
-
 	if (!iov_iter_count(from))
 		return 0;
mm/filemap.c +0 -3
index 1784478270e1..d1b8cd15b2bf 100644
@@ -2920,9 +2920,6 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	loff_t count;
 	int ret;
 
-	if (IS_SWAPFILE(inode))
-		return -ETXTBSY;
-
 	if (!iov_iter_count(from))
 		return 0;
mm/memory.c +0 -4
index 0bccc622e482..e908490f7034 100644
@@ -2357,10 +2357,6 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
 
 	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
 
-	if (vmf->vma->vm_file &&
-	    IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host))
-		return VM_FAULT_SIGBUS;
-
 	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
 	/* Restore original flags so that caller is not surprised */
 	vmf->flags = old_flags;
mm/mmap.c +2 -6
index d681a20eb4ea..77d086139e13 100644
@@ -1461,12 +1461,8 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 		case MAP_SHARED_VALIDATE:
 			if (flags & ~flags_mask)
 				return -EOPNOTSUPP;
-			if (prot & PROT_WRITE) {
-				if (!(file->f_mode & FMODE_WRITE))
-					return -EACCES;
-				if (IS_SWAPFILE(file->f_mapping->host))
-					return -ETXTBSY;
-			}
+			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
+				return -EACCES;
 
 			/*
 			 * Make sure we don't allow writing to an append-only
author
#1 lore raw
Quoted 11 lines · Darrick J. Wong

From: Darrick J. Wong <[email protected]>

In commit dc617f29dbe5 we tried to prevent userspace programs from writing to active swap devices. However, it turns out that userspace hibernation requires the ability to write the hibernation image to a swap device, so revert the write path checks.

Fixes dc617f29dbe5 ("vfs: don't allow writes to swap files")
Reported-by Domenico Andreoli <[email protected]>
Reported-by Marian Klein <[email protected]>
Signed-off-by Darrick J. Wong <[email protected]>

self-NAK, Domenico Andreoli has taken this on. Andrew, could you please drop this patch from your queue?

--D

Quoted 69 lines
---
 fs/block_dev.c |    3 ---
 mm/filemap.c   |    3 ---
 mm/memory.c    |    4 ----
 mm/mmap.c      |    8 ++------
 4 files changed, 2 insertions(+), 16 deletions(-)
fs/block_dev.c +0 -3
index 69bf2fb6f7cd..08b088dac1f0 100644
@@ -2001,9 +2001,6 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (bdev_read_only(I_BDEV(bd_inode)))
 		return -EPERM;
 
-	if (IS_SWAPFILE(bd_inode))
-		return -ETXTBSY;
-
 	if (!iov_iter_count(from))
 		return 0;
mm/filemap.c +0 -3
index 1784478270e1..d1b8cd15b2bf 100644
@@ -2920,9 +2920,6 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	loff_t count;
 	int ret;
 
-	if (IS_SWAPFILE(inode))
-		return -ETXTBSY;
-
 	if (!iov_iter_count(from))
 		return 0;
mm/memory.c +0 -4
index 0bccc622e482..e908490f7034 100644
@@ -2357,10 +2357,6 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
 
 	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
 
-	if (vmf->vma->vm_file &&
-	    IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host))
-		return VM_FAULT_SIGBUS;
-
 	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
 	/* Restore original flags so that caller is not surprised */
 	vmf->flags = old_flags;
mm/mmap.c +2 -6
index d681a20eb4ea..77d086139e13 100644
@@ -1461,12 +1461,8 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 		case MAP_SHARED_VALIDATE:
 			if (flags & ~flags_mask)
 				return -EOPNOTSUPP;
-			if (prot & PROT_WRITE) {
-				if (!(file->f_mode & FMODE_WRITE))
-					return -EACCES;
-				if (IS_SWAPFILE(file->f_mapping->host))
-					return -ETXTBSY;
-			}
+			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
+				return -EACCES;
 
 			/*
 			 * Make sure we don't allow writing to an append-only