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GET /api/patches/2217529/?format=api
{ "id": 2217529, "url": "http://patchwork.ozlabs.org/api/patches/2217529/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-ext4/patch/20260330044334.373480-1-kartikey406@gmail.com/", "project": { "id": 8, "url": "http://patchwork.ozlabs.org/api/projects/8/?format=api", "name": "Linux ext4 filesystem development", "link_name": "linux-ext4", "list_id": "linux-ext4.vger.kernel.org", "list_email": "linux-ext4@vger.kernel.org", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260330044334.373480-1-kartikey406@gmail.com>", "list_archive_url": null, "date": "2026-03-30T04:43:34", "name": "loop: block loop reconfiguration of offset/sizelimit on mounted device", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "767b12ddc45de1f098bd27b707db7b5c35b6229b", "submitter": { "id": 91725, "url": "http://patchwork.ozlabs.org/api/people/91725/?format=api", "name": "Deepanshu Kartikey", "email": "kartikey406@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linux-ext4/patch/20260330044334.373480-1-kartikey406@gmail.com/mbox/", "series": [ { "id": 497950, "url": "http://patchwork.ozlabs.org/api/series/497950/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-ext4/list/?series=497950", "date": "2026-03-30T04:43:34", "name": "loop: block loop reconfiguration of offset/sizelimit on mounted device", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/497950/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2217529/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2217529/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <SRS0=/f8Y=B6=vger.kernel.org=linux-ext4+bounces-15527-patchwork-incoming=ozlabs.org@ozlabs.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linux-ext4@vger.kernel.org" ], "Delivered-To": [ "patchwork-incoming@legolas.ozlabs.org", "patchwork-incoming@ozlabs.org" ], "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=pMK0iePC;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=2404:9400:2221:ea00::3; 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This effectively mutates\nthe data visible to the mounted filesystem, which is equivalent to\nwriting directly to the block device.\n\nWhen bdev_allow_write_mounted is false, direct writes to a mounted\nblock device are blocked via bdev_writes_blocked(). However,\nLOOP_SET_STATUS{64} bypasses this protection because it modifies\nthe loop configuration through an ioctl rather than opening the\nblock device for writing.\n\nFix this by checking bdev_writes_blocked() before allowing changes\nto lo_offset or lo_sizelimit. If the loop device has writes blocked\n(indicating a filesystem is mounted with write protection), return\n-EBUSY. Other loop status fields that do not affect the visible\ndata can still be changed while mounted.\n\nExport bdev_writes_blocked() so it can be used from the loop driver.\n\nSuggested-by: Theodore Ts'o <tytso@mit.edu>\nReported-by: syzbot+fb32afec111a7d61b939@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=fb32afec111a7d61b939\nTested-by: syzbot+fb32afec111a7d61b939@syzkaller.appspotmail.com\nSigned-off-by: Deepanshu Kartikey <kartikey406@gmail.com>\n---\n block/bdev.c | 4 +++-\n drivers/block/loop.c | 12 ++++++++++++\n include/linux/blkdev.h | 1 +\n 3 files changed, 16 insertions(+), 1 deletion(-)", "diff": "diff --git a/block/bdev.c b/block/bdev.c\nindex ed022f8c48c7..96520fac7b2f 100644\n--- a/block/bdev.c\n+++ b/block/bdev.c\n@@ -860,10 +860,12 @@ void blkdev_put_no_open(struct block_device *bdev)\n \tput_device(&bdev->bd_device);\n }\n \n-static bool bdev_writes_blocked(struct block_device *bdev)\n+bool bdev_writes_blocked(struct block_device *bdev)\n {\n \treturn bdev->bd_writers < 0;\n }\n+EXPORT_SYMBOL_GPL(bdev_writes_blocked);\n+\n \n static void bdev_block_writes(struct block_device *bdev)\n {\ndiff --git a/drivers/block/loop.c b/drivers/block/loop.c\nindex 0000913f7efc..3f3a29abad1f 100644\n--- a/drivers/block/loop.c\n+++ b/drivers/block/loop.c\n@@ -1239,6 +1239,18 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)\n \t\tgoto out_unlock;\n \t}\n \n+\t/*\n+\t * Changing lo_offset or lo_sizelimit on a mounted device is\n+\t * equivalent to modifying the block device contents, block\n+\t * this if writes are blocked on the device.\n+\t */\n+\tif ((lo->lo_offset != info->lo_offset ||\n+\t lo->lo_sizelimit != info->lo_sizelimit) &&\n+\t bdev_writes_blocked(lo->lo_device)) {\n+\t\terr = -EBUSY;\n+\t\tgoto out_unlock;\n+\t}\n+\n \tif (lo->lo_offset != info->lo_offset ||\n \t lo->lo_sizelimit != info->lo_sizelimit) {\n \t\tsize_changed = true;\ndiff --git a/include/linux/blkdev.h b/include/linux/blkdev.h\nindex d463b9b5a0a5..6b908e9dd035 100644\n--- a/include/linux/blkdev.h\n+++ b/include/linux/blkdev.h\n@@ -820,6 +820,7 @@ static inline bool bdev_read_only(struct block_device *bdev)\n \treturn bdev_test_flag(bdev, BD_READ_ONLY) || get_disk_ro(bdev->bd_disk);\n }\n \n+bool bdev_writes_blocked(struct block_device *bdev);\n bool set_capacity_and_notify(struct gendisk *disk, sector_t size);\n void disk_force_media_change(struct gendisk *disk);\n void bdev_mark_dead(struct block_device *bdev, bool surprise);\n", "prefixes": [] }