From e28cc71572da38a5a12c1cfe4d7032017adccf69 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 4 Jan 2006 16:20:40 -0800 Subject: [PATCH] Relax the rw_verify_area() error checking. In particular, allow over-large read- or write-requests to be downgraded to a more reasonable range, rather than considering them outright errors. We want to protect lower layers from (the sadly all too common) overflow conditions, but prefer to do so by chopping the requests up, rather than just refusing them outright. Cc: Peter Anvin Cc: Ulrich Drepper Cc: Andi Kleen Cc: Al Viro Signed-off-by: Linus Torvalds --- arch/mips/kernel/linux32.c | 4 ++-- fs/compat.c | 2 +- fs/read_write.c | 34 +++++++++++++++++++++++++--------- 3 files changed, 28 insertions(+), 12 deletions(-) diff --git a/arch/mips/kernel/linux32.c b/arch/mips/kernel/linux32.c index 330cf84d21fe..60353f5acc48 100644 --- a/arch/mips/kernel/linux32.c +++ b/arch/mips/kernel/linux32.c @@ -420,7 +420,7 @@ asmlinkage ssize_t sys32_pread(unsigned int fd, char * buf, goto out; pos = merge_64(a4, a5); ret = rw_verify_area(READ, file, &pos, count); - if (ret) + if (ret < 0) goto out; ret = -EINVAL; if (!file->f_op || !(read = file->f_op->read)) @@ -455,7 +455,7 @@ asmlinkage ssize_t sys32_pwrite(unsigned int fd, const char * buf, goto out; pos = merge_64(a4, a5); ret = rw_verify_area(WRITE, file, &pos, count); - if (ret) + if (ret < 0) goto out; ret = -EINVAL; if (!file->f_op || !(write = file->f_op->write)) diff --git a/fs/compat.c b/fs/compat.c index 818634120b69..55ac0324aaf1 100644 --- a/fs/compat.c +++ b/fs/compat.c @@ -1170,7 +1170,7 @@ static ssize_t compat_do_readv_writev(int type, struct file *file, } ret = rw_verify_area(type, file, pos, tot_len); - if (ret) + if (ret < 0) goto out; fnv = NULL; diff --git a/fs/read_write.c b/fs/read_write.c index a091ee4f430d..df3468a22fea 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -182,22 +183,33 @@ bad: } #endif +/* + * rw_verify_area doesn't like huge counts. We limit + * them to something that fits in "int" so that others + * won't have to do range checks all the time. + */ +#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK) int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count) { struct inode *inode; loff_t pos; - if (unlikely(count > INT_MAX)) + if (unlikely((ssize_t) count < 0)) goto Einval; pos = *ppos; if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) goto Einval; inode = file->f_dentry->d_inode; - if (inode->i_flock && MANDATORY_LOCK(inode)) - return locks_mandatory_area(read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE, inode, file, pos, count); - return 0; + if (inode->i_flock && MANDATORY_LOCK(inode)) { + int retval = locks_mandatory_area( + read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE, + inode, file, pos, count); + if (retval < 0) + return retval; + } + return count > MAX_RW_COUNT ? MAX_RW_COUNT : count; Einval: return -EINVAL; @@ -244,7 +256,8 @@ ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos) return -EFAULT; ret = rw_verify_area(READ, file, pos, count); - if (!ret) { + if (ret >= 0) { + count = ret; ret = security_file_permission (file, MAY_READ); if (!ret) { if (file->f_op->read) @@ -295,7 +308,8 @@ ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_ return -EFAULT; ret = rw_verify_area(WRITE, file, pos, count); - if (!ret) { + if (ret >= 0) { + count = ret; ret = security_file_permission (file, MAY_WRITE); if (!ret) { if (file->f_op->write) @@ -497,7 +511,7 @@ static ssize_t do_readv_writev(int type, struct file *file, } ret = rw_verify_area(type, file, pos, tot_len); - if (ret) + if (ret < 0) goto out; ret = security_file_permission(file, type == READ ? MAY_READ : MAY_WRITE); if (ret) @@ -653,8 +667,9 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos, if (!(in_file->f_mode & FMODE_PREAD)) goto fput_in; retval = rw_verify_area(READ, in_file, ppos, count); - if (retval) + if (retval < 0) goto fput_in; + count = retval; retval = security_file_permission (in_file, MAY_READ); if (retval) @@ -674,8 +689,9 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos, goto fput_out; out_inode = out_file->f_dentry->d_inode; retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count); - if (retval) + if (retval < 0) goto fput_out; + count = retval; retval = security_file_permission (out_file, MAY_WRITE); if (retval) -- 2.20.1