From: Ahmad Fatoum <ahmad@a3f.at>
To: barebox@lists.infradead.org
Cc: Ahmad Fatoum <ahmad@a3f.at>, Xogium <contact@xogium.me>
Subject: [PATCH master] fs: fix NULL pointer dereference of fsdrv->truncate for read-only FS
Date: Wed, 7 Jul 2021 00:08:09 +0200 [thread overview]
Message-ID: <20210706220809.729815-1-ahmad@a3f.at> (raw)
fsdrv->truncate is dereferenced at times without checking for NULL before,
leading to crashes, e.g. doing:
edit -o /mnt/myext4/FILE some text
on ext4 crashes. Fix this by returning -EROFS when truncate is unimplemented.
Reported-by: Xogium <contact@xogium.me>
Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
---
fs/fs.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/fs/fs.c b/fs/fs.c
index a9dbf1dd4e2f..2f4b642b3952 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -208,9 +208,15 @@ int creat(const char *pathname, mode_t mode)
}
EXPORT_SYMBOL(creat);
+static int fsdev_truncate(struct device_d *dev, FILE *f, loff_t length)
+{
+ struct fs_driver_d *fsdrv = f->fsdev->driver;
+
+ return fsdrv->truncate ? fsdrv->truncate(&f->fsdev->dev, f, length) : -EROFS;
+}
+
int ftruncate(int fd, loff_t length)
{
- struct fs_driver_d *fsdrv;
FILE *f = fd_to_file(fd);
int ret;
@@ -220,9 +226,7 @@ int ftruncate(int fd, loff_t length)
if (f->size == FILE_SIZE_STREAM)
return 0;
- fsdrv = f->fsdev->driver;
-
- ret = fsdrv->truncate(&f->fsdev->dev, f, length);
+ ret = fsdev_truncate(&f->fsdev->dev, f, length);
if (ret) {
errno = -ret;
return ret;
@@ -332,7 +336,7 @@ static ssize_t __write(FILE *f, const void *buf, size_t count)
assert_command_context();
if (f->size != FILE_SIZE_STREAM && f->pos + count > f->size) {
- ret = fsdrv->truncate(&f->fsdev->dev, f, f->pos + count);
+ ret = fsdev_truncate(&f->fsdev->dev, f, f->pos + count);
if (ret) {
if (ret != -ENOSPC)
goto out;
@@ -2463,7 +2467,7 @@ int open(const char *pathname, int flags, ...)
}
if (flags & O_TRUNC) {
- error = fsdrv->truncate(&fsdev->dev, f, 0);
+ error = fsdev_truncate(&fsdev->dev, f, 0);
f->size = 0;
inode->i_size = 0;
if (error)
--
2.32.0
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