Messages in this thread Patch in this message |  | | | Date | Fri, 24 Mar 2006 20:12:10 -0800 | | From | Greg KH <> | | Subject | [PATCH 08/08] Fix ext2 readdir f_pos re-validation logic |
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From: Al Viro <viro@ftp.linux.org.uk>
This fixes not one, but _two_, silly (but admittedly hard to hit) bugs in the ext2 filesystem "readdir()" function. It also cleans up the code to avoid the unnecessary goto mess.
The bugs were related to re-valiating the f_pos value after somebody had either done an "lseek()" on the directory to an invalid offset, or when the offset had become invalid due to a file being unlinked in the directory. The code would not only set the f_version too eagerly, it would also not update f_pos appropriately for when the offset fixup took place.
When that happened, we'd occasionally subsequently fail the readdir() even when we shouldn't (no real harm done, but an ugly printk, and obviously you would end up not necessarily seeing all entries).
Thanks to Masoud Sharbiani <masouds@google.com> who noticed the problem and had a test-case for it, and also fixed up a thinko in the first version of this patch.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Masoud Sharbiani <masouds@google.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- fs/ext2/dir.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-) 2d7f2ea9c989853310c7f6e8be52cc090cc8e66b --- linux-2.6.15.6.orig/fs/ext2/dir.c +++ linux-2.6.15.6/fs/ext2/dir.c @@ -256,11 +256,10 @@ ext2_readdir (struct file * filp, void * unsigned long npages = dir_pages(inode); unsigned chunk_mask = ~(ext2_chunk_size(inode)-1); unsigned char *types = NULL; - int need_revalidate = (filp->f_version != inode->i_version); - int ret; + int need_revalidate = filp->f_version != inode->i_version; if (pos > inode->i_size - EXT2_DIR_REC_LEN(1)) - goto success; + return 0; if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE)) types = ext2_filetype_table; @@ -275,12 +274,15 @@ ext2_readdir (struct file * filp, void * "bad page in #%lu", inode->i_ino); filp->f_pos += PAGE_CACHE_SIZE - offset; - ret = -EIO; - goto done; + return -EIO; } kaddr = page_address(page); - if (need_revalidate) { - offset = ext2_validate_entry(kaddr, offset, chunk_mask); + if (unlikely(need_revalidate)) { + if (offset) { + offset = ext2_validate_entry(kaddr, offset, chunk_mask); + filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset; + } + filp->f_version = inode->i_version; need_revalidate = 0; } de = (ext2_dirent *)(kaddr+offset); @@ -289,9 +291,8 @@ ext2_readdir (struct file * filp, void * if (de->rec_len == 0) { ext2_error(sb, __FUNCTION__, "zero-length directory entry"); - ret = -EIO; ext2_put_page(page); - goto done; + return -EIO; } if (de->inode) { int over; @@ -306,19 +307,14 @@ ext2_readdir (struct file * filp, void * le32_to_cpu(de->inode), d_type); if (over) { ext2_put_page(page); - goto success; + return 0; } } filp->f_pos += le16_to_cpu(de->rec_len); } ext2_put_page(page); } - -success: - ret = 0; -done: - filp->f_version = inode->i_version; - return ret; + 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/
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