Messages in this thread Patch in this message | | | Date | Thu, 17 Sep 2009 15:07:26 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [RFC][PATCH][bugfix] more checks for negative f_pos handling v3 |
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Very sorry...reflesh miss. == From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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/<pid>/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: - fixed bug in rw_verify_area (it cannot be compiled)
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- drivers/char/mem.c | 23 +++++++++++++---------- fs/proc/base.c | 2 ++ fs/read_write.c | 20 ++++++++++++++++++-- include/linux/fs.h | 2 ++ 4 files changed, 35 insertions(+), 12 deletions(-)
Index: mmotm-2.6.31-Sep14/fs/read_write.c =================================================================== --- mmotm-2.6.31-Sep14.orig/fs/read_write.c +++ mmotm-2.6.31-Sep14/fs/read_write.c @@ -205,6 +205,16 @@ bad: } #endif +static bool +__negative_fpos_check(struct inode *inode, loff_t pos, size_t count) +{ + if (pos + count < pos) + return -EOVERFLOW; + if (IS_VERYBIG(inode)) + return 0; + return -EINVAL; +} + /* * rw_verify_area doesn't like huge counts. We limit * them to something that fits in "int" so that others @@ -222,8 +232,11 @@ 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( Index: mmotm-2.6.31-Sep14/include/linux/fs.h =================================================================== --- mmotm-2.6.31-Sep14.orig/include/linux/fs.h +++ mmotm-2.6.31-Sep14/include/linux/fs.h @@ -231,6 +231,7 @@ 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 /* Allow file's loff_t can be negative */ /* * Note that nosuid etc flags are inode-specific: setting some file-system @@ -265,6 +266,7 @@ 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. */ Index: mmotm-2.6.31-Sep14/drivers/char/mem.c =================================================================== --- mmotm-2.6.31-Sep14.orig/drivers/char/mem.c +++ mmotm-2.6.31-Sep14/drivers/char/mem.c @@ -825,22 +825,23 @@ static const struct memdev { const char *name; const struct file_operations *fops; struct backing_dev_info *dev_info; + bool verybig; } devlist[] = { - [ 1] = { "mem", &mem_fops, &directly_mappable_cdev_bdi }, + [1] = { "mem", &mem_fops, &directly_mappable_cdev_bdi, true }, #ifdef CONFIG_DEVKMEM - [ 2] = { "kmem", &kmem_fops, &directly_mappable_cdev_bdi }, + [2] = { "kmem", &kmem_fops, &directly_mappable_cdev_bdi, true }, #endif - [ 3] = {"null", &null_fops, NULL }, + [3] = {"null", &null_fops, NULL, false }, #ifdef CONFIG_DEVPORT - [ 4] = { "port", &port_fops, NULL }, + [4] = { "port", &port_fops, NULL, false }, #endif - [ 5] = { "zero", &zero_fops, &zero_bdi }, - [ 6] = { "full", &full_fops, NULL }, - [ 7] = { "random", &random_fops, NULL }, - [ 9] = { "urandom", &urandom_fops, NULL }, - [11] = { "kmsg", &kmsg_fops, NULL }, + [5] = { "zero", &zero_fops, &zero_bdi, false }, + [6] = { "full", &full_fops, NULL, false }, + [7] = { "random", &random_fops, NULL, false }, + [9] = { "urandom", &urandom_fops, NULL, false }, + [11] = { "kmsg", &kmsg_fops, NULL, false }, #ifdef CONFIG_CRASH_DUMP - [12] = { "oldmem", &oldmem_fops, NULL }, + [12] = { "oldmem", &oldmem_fops, NULL, false }, #endif }; @@ -868,6 +869,8 @@ static int memory_open(struct inode *ino ret = dev->fops->open(inode, filp); else ret = 0; + if (dev->verybig) + inode->i_flags |= S_VERYBIG; out: unlock_kernel(); return ret; Index: mmotm-2.6.31-Sep14/fs/proc/base.c =================================================================== --- mmotm-2.6.31-Sep14.orig/fs/proc/base.c +++ mmotm-2.6.31-Sep14/fs/proc/base.c @@ -779,6 +779,8 @@ 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-pf-range */ + inode->i_flags |= S_VERYBIG; return 0; }
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