kernel/linux.git/drivers/cdrom/cdrom.c, branch v6.1.175

cdrom, scsi: sr: propagate read-only status to block layer via set_disk_ro()

2026-06-01T15:39:27+00:00

[ Upstream commit 0898a817621a2f0cddca8122d9b974003fe5036d ] The cdrom core never calls set_disk_ro() for a registered device, so BLKROGET on a CD-ROM device always returns 0 (writable), even when the drive has no write capabilities and writes will inevitably fail. This causes problems for userspace that relies on BLKROGET to determine whether a block device is read-only. For example, systemd's loop device setup uses BLKROGET to decide whether to create a loop device with LO_FLAGS_READ_ONLY. Without the read-only flag, writes pass through the loop device to the CD-ROM and fail with I/O errors. systemd-fsck similarly checks BLKROGET to decide whether to run fsck in no-repair mode (-n). The write-capability bits in cdi->mask come from two different sources: CDC_DVD_RAM and CDC_CD_RW are populated by the driver from the MODE SENSE capabilities page (page 0x2A) before register_cdrom() is called, while CDC_MRW_W and CDC_RAM require the MMC GET CONFIGURATION command and were only probed by cdrom_open_write() at device open time. This meant that any attempt to compute the writable state from the full mask at probe time was incorrect, because the GET CONFIGURATION bits were still unset (and cdi->mask is initialized such that capabilities are assumed present). Fix this by factoring the GET CONFIGURATION probing out of cdrom_open_write() into a new exported helper, cdrom_probe_write_features(), and having sr call it from sr_probe() right after get_capabilities() has populated the MODE SENSE bits. register_cdrom() then calls set_disk_ro() based on the full write-capability mask (CDC_DVD_RAM | CDC_MRW_W | CDC_RAM | CDC_CD_RW) so the block layer reflects the drive's actual write support. The feature queries used (CDF_MRW and CDF_RWRT via GET CONFIGURATION with RT=00) report drive-level capabilities that are persistent across media, so a single probe before register_cdrom() is sufficient and the redundant probe at open time is dropped. With set_disk_ro() now accurate, the long-vestigial cd->writeable flag in sr can go: get_capabilities() used to set cd->writeable based on the same four mask bits, but because CDC_MRW_W and CDC_RAM default to "capability present" in cdi->mask and aren't touched by MODE SENSE, the condition that gated cd->writeable was always true, making it unconditionally 1. Replace the corresponding gate in sr_init_command() with get_disk_ro(cd->disk), which turns a previously no-op check into a real one and also catches kernel-internal bio writers that bypass blkdev_write_iter()'s bdev_read_only() check. The sd driver (SCSI disks) does not have this problem because it checks the MODE SENSE Write Protect bit and calls set_disk_ro() accordingly. The sr driver cannot use the same approach because the MMC specification does not define the WP bit in the MODE SENSE device-specific parameter byte for CD-ROM devices. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Daan De Meyer Reviewed-by: Phillip Potter Reviewed-by: Martin K. Petersen Signed-off-by: Phillip Potter Link: https://patch.msgid.link/20260427210139.1400-2-phil@philpotter.co.uk Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

cdrom: rearrange last_media_change check to avoid unintentional overflow

2024-07-11T10:47:10+00:00

[ Upstream commit efb905aeb44b0e99c0e6b07865b1885ae0471ebf ] When running syzkaller with the newly reintroduced signed integer wrap sanitizer we encounter this splat: [ 366.015950] UBSAN: signed-integer-overflow in ../drivers/cdrom/cdrom.c:2361:33 [ 366.021089] -9223372036854775808 - 346321 cannot be represented in type '__s64' (aka 'long long') [ 366.025894] program syz-executor.4 is using a deprecated SCSI ioctl, please convert it to SG_IO [ 366.027502] CPU: 5 PID: 28472 Comm: syz-executor.7 Not tainted 6.8.0-rc2-00035-gb3ef86b5a957 #1 [ 366.027512] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 366.027518] Call Trace: [ 366.027523] [ 366.027533] dump_stack_lvl+0x93/0xd0 [ 366.027899] handle_overflow+0x171/0x1b0 [ 366.038787] ata1.00: invalid multi_count 32 ignored [ 366.043924] cdrom_ioctl+0x2c3f/0x2d10 [ 366.063932] ? __pm_runtime_resume+0xe6/0x130 [ 366.071923] sr_block_ioctl+0x15d/0x1d0 [ 366.074624] ? __pfx_sr_block_ioctl+0x10/0x10 [ 366.077642] blkdev_ioctl+0x419/0x500 [ 366.080231] ? __pfx_blkdev_ioctl+0x10/0x10 ... Historically, the signed integer overflow sanitizer did not work in the kernel due to its interaction with `-fwrapv` but this has since been changed [1] in the newest version of Clang. It was re-enabled in the kernel with Commit 557f8c582a9ba8ab ("ubsan: Reintroduce signed overflow sanitizer"). Let's rearrange the check to not perform any arithmetic, thus not tripping the sanitizer. Link: https://github.com/llvm/llvm-project/pull/82432 [1] Closes: https://github.com/KSPP/linux/issues/354 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt Link: https://lore.kernel.org/lkml/20240507-b4-sio-ata1-v1-1-810ffac6080a@google.com Reviewed-by: Phillip Potter Link: https://lore.kernel.org/lkml/ZjqU0fbzHrlnad8D@equinox Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20240507222520.1445-2-phil@philpotter.co.uk Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

cdrom: remove obsolete TODO list

2022-05-16T00:31:28+00:00

The TODO list in drivers/cdrom/cdrom.c has a single entry containing obsolete information, unchanged since the first git commit over 17 years ago, and probably longer. Remove this list from the comment to prevent confusion in future. Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20220515205833.944139-6-phil@philpotter.co.uk Signed-off-by: Jens Axboe

cdrom: remove the unused driver specific disc change ioctl

2022-05-16T00:31:28+00:00

This was only used by the ide-cd driver, which went away in commit b7fb14d3ac63 ("ide: remove the legacy ide driver") so we might as well take advantage of that and get rid of this hook as well. Cc: Christoph Hellwig Cc: Jens Axboe Cc: Phillip Potter Signed-off-by: Paul Gortmaker Link: https://lore.kernel.org/all/20220427132436.12795-2-paul.gortmaker@windriver.com Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20220515205833.944139-3-phil@philpotter.co.uk Signed-off-by: Jens Axboe

cdrom: make EXPORT_SYMBOL follow exported function

2022-05-16T00:31:28+00:00

Currently, some EXPORT_SYMBOL declarations do not follow the exported function, which affects the readability of the code. To maintain consistency, move these EXPORT_SYMBOL declarations to the correct position to improve the readability of the code. Signed-off-by: Enze Li Link: https://lore.kernel.org/all/20220406090337.1116708-1-lienze@kylinos.cn Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20220515205833.944139-2-phil@philpotter.co.uk Signed-off-by: Jens Axboe

cdrom: remove unused variable

2022-04-06T14:47:52+00:00

The clang static analyzer reports the following warning, File: drivers/cdrom/cdrom.c Warning: line 1380, column 7 Although the value stored to 'status' is used in enclosing expression, the value is never actually read from 'status' Remove the unused variable to eliminate the warning. Signed-off-by: Enze Li Link: https://lore.kernel.org/all/20220401032623.293666-1-lienze@kylinos.cn Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20220401211842.2088096-1-phil@philpotter.co.uk Signed-off-by: Jens Axboe

scsi: core: Remove

2022-03-02T03:21:50+00:00

This header is empty now except for an include of , so remove it. Link: https://lore.kernel.org/r/20220224175552.988286-9-hch@lst.de Reviewed-by: Bart Van Assche Reviewed-by: John Garry Signed-off-by: Christoph Hellwig Signed-off-by: Martin K. Petersen

cdrom: simplify subdirectory registration with register_sysctl()

2022-01-22T06:33:35+00:00

There is no need to user boiler plate code to specify a set of base directories we're going to stuff sysctls under. Simplify this by using register_sysctl() and specifying the directory path directly. // pycocci sysctl-subdir-register-sysctl-simplify.cocci PATH @c1@ expression E1; identifier subdir, sysctls; @@ static struct ctl_table subdir[] = { { .procname = E1, .maxlen = 0, .mode = 0555, .child = sysctls, }, { } }; @c2@ identifier c1.subdir; expression E2; identifier base; @@ static struct ctl_table base[] = { { .procname = E2, .maxlen = 0, .mode = 0555, .child = subdir, }, { } }; @c3@ identifier c2.base; identifier header; @@ header = register_sysctl_table(base); @r1 depends on c1 && c2 && c3@ expression c1.E1; identifier c1.subdir, c1.sysctls; @@ -static struct ctl_table subdir[] = { - { - .procname = E1, - .maxlen = 0, - .mode = 0555, - .child = sysctls, - }, - { } -}; @r2 depends on c1 && c2 && c3@ identifier c1.subdir; expression c2.E2; identifier c2.base; @@ -static struct ctl_table base[] = { - { - .procname = E2, - .maxlen = 0, - .mode = 0555, - .child = subdir, - }, - { } -}; @initialize:python@ @@ def make_my_fresh_expression(s1, s2): return '"' + s1.strip('"') + "/" + s2.strip('"') + '"' @r3 depends on c1 && c2 && c3@ expression c1.E1; identifier c1.sysctls; expression c2.E2; identifier c2.base; identifier c3.header; fresh identifier E3 = script:python(E2, E1) { make_my_fresh_expression(E2, E1) }; @@ header = -register_sysctl_table(base); +register_sysctl(E3, sysctls); Generated-by: Coccinelle SmPL Link: https://lkml.kernel.org/r/20211123202422.819032-8-mcgrof@kernel.org Signed-off-by: Luis Chamberlain Cc: Al Viro Cc: Amir Goldstein Cc: Andy Shevchenko Cc: Antti Palosaari Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Benjamin LaHaise Cc: Clemens Ladisch Cc: David Airlie Cc: "Eric W. Biederman" Cc: Greg Kroah-Hartman Cc: Iurii Zaikin Cc: Jani Nikula Cc: Jan Kara Cc: Joel Becker Cc: Joonas Lahtinen Cc: Joseph Qi Cc: Julia Lawall Cc: Kees Cook Cc: Lukas Middendorf Cc: Mark Fasheh Cc: Paul Turner Cc: Peter Zijlstra Cc: Petr Mladek Cc: Phillip Potter Cc: Qing Wang Cc: Rodrigo Vivi Cc: Sebastian Reichel Cc: Sergey Senozhatsky Cc: Stephen Kitt Cc: Tetsuo Handa Cc: Xiaoming Ni Cc: Douglas Gilbert Cc: James E.J. Bottomley Cc: Jani Nikula Cc: John Ogness Cc: Martin K. Petersen Cc: "Rafael J. Wysocki" Cc: Steven Rostedt (VMware) Cc: Suren Baghdasaryan Cc: "Theodore Ts'o" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cdrom: Remove redundant variable and its assignment

2021-10-21T14:23:09+00:00

Variable is not used in functions, and its assignment is redundant too. So it should be deleted. Also the inner-most set of parentheses is no longer needed. The clang_analyzer complains as follows: drivers/cdrom/cdrom.c:877: warning: Although the value stored to 'ret' is used in the enclosing expression, the value is never actually read from 'ret'. Reported-by: Zeal Robot Signed-off-by: luo penghao Link: https://lore.kernel.org/all/20211020024229.1036219-1-luo.penghao@zte.com.cn Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20211021074621.901-1-phil@philpotter.co.uk Signed-off-by: Jens Axboe

drivers/cdrom: improved ioctl for media change detection

2021-09-15T02:05:26+00:00

The current implementation of the CDROM_MEDIA_CHANGED ioctl relies on global state, meaning that only one process can detect a disc change while the ioctl call will return 0 for other calling processes afterwards (see bug 213267). This introduces a new cdrom ioctl, CDROM_TIMED_MEDIA_CHANGE, that works by maintaining a timestamp of the last detected disc change instead of a boolean flag: Processes calling this ioctl command can provide a timestamp of the last disc change known to them and receive an indication whether the disc was changed since then and the updated timestamp. I considered fixing the buggy behavior in the original CDROM_MEDIA_CHANGED ioctl but that would require maintaining state for each calling process in the kernel, which seems like a worse solution than introducing this new ioctl. Signed-off-by: Lukas Prediger Link: https://lore.kernel.org/all/20210912191207.74449-1-lumip@lumip.de Signed-off-by: Phillip Potter Link: https://lore.kernel.org/r/20210913230942.1188-1-phil@philpotter.co.uk Signed-off-by: Jens Axboe