From: KAMEZAWA Hiroyuki Now, rw_verify_area() checsk f_pos is negative or not. And if negative, returns -EINVAL. But, some special files as /dev/(k)mem and /proc//mem etc.. has negative offsets. And we can't do any access via read/write to the file(device). This patch introduce a flag S_VERYBIG and allow negative file offsets. Changelog: v4->v5 - clean up patches dor /dev/mem. - rebased onto 2.6.32-rc1 Changelog: v3->v4 - make changes in mem.c aligned. - change __negative_fpos_check() to return int. - fixed bug in "pos" check. - added comments. Changelog: v2->v3 - fixed bug in rw_verify_area (it cannot be compiled) CC: Heiko Carstens Reviewed-by: Wu Fengguang Signed-off-by: KAMEZAWA Hiroyuki --- drivers/char/mem.c | 4 ++++ fs/proc/base.c | 2 ++ fs/read_write.c | 22 ++++++++++++++++++++-- include/linux/fs.h | 2 ++ 4 files changed, 28 insertions(+), 2 deletions(-) --- linux-mm.orig/fs/read_write.c 2010-01-13 21:23:04.000000000 +0800 +++ linux-mm/fs/read_write.c 2010-01-13 21:23:52.000000000 +0800 @@ -205,6 +205,21 @@ bad: } #endif +static int +__negative_fpos_check(struct inode *inode, loff_t pos, size_t count) +{ + /* + * pos or pos+count is negative here, check overflow. + * too big "count" will be caught in rw_verify_area(). + */ + if ((pos < 0) && (pos + count < pos)) + return -EOVERFLOW; + /* If !VERYBIG inode, negative pos(pos+count) is not allowed */ + if (!IS_VERYBIG(inode)) + return -EINVAL; + return 0; +} + /* * rw_verify_area doesn't like huge counts. We limit * them to something that fits in "int" so that others @@ -222,8 +237,11 @@ int rw_verify_area(int read_write, struc if (unlikely((ssize_t) count < 0)) return retval; pos = *ppos; - if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) - return retval; + if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) { + retval = __negative_fpos_check(inode, pos, count); + if (retval) + return retval; + } if (unlikely(inode->i_flock && mandatory_lock(inode))) { retval = locks_mandatory_area( --- linux-mm.orig/include/linux/fs.h 2010-01-13 21:23:04.000000000 +0800 +++ linux-mm/include/linux/fs.h 2010-01-13 21:31:02.000000000 +0800 @@ -235,6 +235,7 @@ struct inodes_stat_t { #define S_NOCMTIME 128 /* Do not update file c/mtime */ #define S_SWAPFILE 256 /* Do not truncate: swapon got its bmaps */ #define S_PRIVATE 512 /* Inode is fs-internal */ +#define S_VERYBIG 1024 /* Inode is huge: treat loff_t as unsigned */ /* * Note that nosuid etc flags are inode-specific: setting some file-system @@ -269,6 +270,7 @@ struct inodes_stat_t { #define IS_NOCMTIME(inode) ((inode)->i_flags & S_NOCMTIME) #define IS_SWAPFILE(inode) ((inode)->i_flags & S_SWAPFILE) #define IS_PRIVATE(inode) ((inode)->i_flags & S_PRIVATE) +#define IS_VERYBIG(inode) ((inode)->i_flags & S_VERYBIG) /* the read-only stuff doesn't really belong here, but any other place is probably as bad and I don't want to create yet another include file. */ --- linux-mm.orig/drivers/char/mem.c 2010-01-13 21:23:11.000000000 +0800 +++ linux-mm/drivers/char/mem.c 2010-01-13 21:27:28.000000000 +0800 @@ -861,6 +861,10 @@ static int memory_open(struct inode *ino if (dev->dev_info) filp->f_mapping->backing_dev_info = dev->dev_info; + /* Is /dev/mem or /dev/kmem ? */ + if (dev->dev_info == &directly_mappable_cdev_bdi) + inode->i_flags |= S_VERYBIG; + if (dev->fops->open) return dev->fops->open(inode, filp); --- linux-mm.orig/fs/proc/base.c 2010-01-13 21:23:04.000000000 +0800 +++ linux-mm/fs/proc/base.c 2010-01-13 21:27:51.000000000 +0800 @@ -861,6 +861,8 @@ static const struct file_operations proc static int mem_open(struct inode* inode, struct file* file) { file->private_data = (void*)((long)current->self_exec_id); + /* this file is read only and we can catch out-of-range */ + inode->i_flags |= S_VERYBIG; return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/