| Message ID | 20230728065819.139694-1-oleksandr@redhat.com |
|---|---|
| Headers | show |
| Series | scsi: qedf: sanitise uaccess | expand |
On pátek 28. července 2023 8:58:16 CEST Oleksandr Natalenko wrote: > qedf driver, debugfs part of it specifically, touches __user pointers > directly for printing out info to userspace via sprintf(), which may > cause crash like this: > > BUG: unable to handle kernel paging request at 00007ffd1d6b43a0 > IP: [<ffffffffaa7a882a>] string.isra.7+0x6a/0xf0 > Oops: 0003 [#1] SMP > Call Trace: > [<ffffffffaa7a9f31>] vsnprintf+0x201/0x6a0 > [<ffffffffaa7aa556>] sprintf+0x56/0x80 > [<ffffffffc04227ed>] qedf_dbg_stop_io_on_error_cmd_read+0x6d/0x90 [qedf] > [<ffffffffaa65bb2f>] vfs_read+0x9f/0x170 > [<ffffffffaa65cb82>] SyS_pread64+0x92/0xc0 > > Avoid this by preparing the info in a kernel buffer first, either > allocated on stack for small printouts, or via vmalloc() for big ones, > and then copying it to the userspace properly. > > Previous submission is an RFC: [1]. There are no code changes since > then. The RFC prefix is dropped. The Tested-by tag from Laurence is > added. > > There's similar submission from Saurav [2], but we agreed I could nack > it and proceed with my one. > > [1] https://lore.kernel.org/linux-scsi/20230724120241.40495-1-oleksandr@redhat.com/ > [2] https://lore.kernel.org/linux-scsi/20230726101236.11922-1-skashyap@marvell.com/ > > Oleksandr Natalenko (3): > scsi: qedf: do not touch __user pointer in > qedf_dbg_stop_io_on_error_cmd_read() directly > scsi: qedf: do not touch __user pointer in qedf_dbg_debug_cmd_read() > directly > scsi: qedf: do not touch __user pointer in qedf_dbg_fp_int_cmd_read() > directly > > drivers/scsi/qedf/qedf_dbg.h | 2 ++ > drivers/scsi/qedf/qedf_debugfs.c | 35 +++++++++++++++++++------------- > 2 files changed, 23 insertions(+), 14 deletions(-) > > Oops, I forgot to add: Reviewed-by: Laurence Oberman <loberman@redhat.com> as per [1]. My ask to the maintainer to add it if the submission is accepted, or let me know if I should do a v2 instead. [1] https://lore.kernel.org/linux-scsi/4f35b02968a18e636e1689c9d52729ef63a438f9.camel@redhat.com/
Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
From: Oleksandr Natalenko > Sent: 28 July 2023 07:58 > > The qedf_dbg_debug_cmd_read() function invokes sprintf() > directly on a __user pointer, which may crash the kernel. ^^^ will > > Avoid doing that by using a small on-stack buffer for sprintf() > and then calling simple_read_from_buffer() which does a proper > copy_to_user() call. ... > diff --git a/drivers/scsi/qedf/qedf_debugfs.c b/drivers/scsi/qedf/qedf_debugfs.c > index 4d1b99569d490..f910af0029a2c 100644 > --- a/drivers/scsi/qedf/qedf_debugfs.c > +++ b/drivers/scsi/qedf/qedf_debugfs.c > @@ -138,15 +138,14 @@ qedf_dbg_debug_cmd_read(struct file *filp, char __user *buffer, size_t count, > loff_t *ppos) > { > int cnt; > + char cbuf[35]; Why 35? I pick a multiple of 8 that if 'enough. > struct qedf_dbg_ctx *qedf_dbg = > (struct qedf_dbg_ctx *)filp->private_data; > > QEDF_INFO(qedf_dbg, QEDF_LOG_DEBUGFS, "debug mask=0x%x\n", qedf_debug); > - cnt = sprintf(buffer, "debug mask = 0x%x\n", qedf_debug); > + cnt = sprintf(cbuf, "debug mask = 0x%x\n", qedf_debug); Use scnprintf() to be sure it doesn't overflow. Much safer if someone does a quick update or copies the code. David > > - cnt = min_t(int, count, cnt - *ppos); > - *ppos += cnt; > - return cnt; > + return simple_read_from_buffer(buffer, count, ppos, cbuf, cnt); > } > > static ssize_t > -- > 2.41.0 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
Hello/ On pátek 28. července 2023 17:26:11 CEST David Laight wrote: > From: Oleksandr Natalenko > > Sent: 28 July 2023 07:58 > > > > The qedf_dbg_debug_cmd_read() function invokes sprintf() > > directly on a __user pointer, which may crash the kernel. > ^^^ will I don't think it is 100% guaranteed, but for sure this is not a correct behaviour. > > > > Avoid doing that by using a small on-stack buffer for sprintf() > > and then calling simple_read_from_buffer() which does a proper > > copy_to_user() call. > ... > > diff --git a/drivers/scsi/qedf/qedf_debugfs.c b/drivers/scsi/qedf/qedf_debugfs.c > > index 4d1b99569d490..f910af0029a2c 100644 > > --- a/drivers/scsi/qedf/qedf_debugfs.c > > +++ b/drivers/scsi/qedf/qedf_debugfs.c > > @@ -138,15 +138,14 @@ qedf_dbg_debug_cmd_read(struct file *filp, char __user *buffer, size_t count, > > loff_t *ppos) > > { > > int cnt; > > + char cbuf[35]; > > Why 35? > I pick a multiple of 8 that if 'enough. OK, I overestimated this, it should have been 27, but I'll make it 32 to be a multiple of 8. Thanks. > > struct qedf_dbg_ctx *qedf_dbg = > > (struct qedf_dbg_ctx *)filp->private_data; > > > > QEDF_INFO(qedf_dbg, QEDF_LOG_DEBUGFS, "debug mask=0x%x\n", qedf_debug); > > - cnt = sprintf(buffer, "debug mask = 0x%x\n", qedf_debug); > > + cnt = sprintf(cbuf, "debug mask = 0x%x\n", qedf_debug); > > Use scnprintf() to be sure it doesn't overflow. > Much safer if someone does a quick update or copies the code. > > David > > > > > - cnt = min_t(int, count, cnt - *ppos); > > - *ppos += cnt; > > - return cnt; > > + return simple_read_from_buffer(buffer, count, ppos, cbuf, cnt); > > } > > > > static ssize_t > > -- > > 2.41.0 > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) > >
qedf driver, debugfs part of it specifically, touches __user pointers directly for printing out info to userspace via sprintf(), which may cause crash like this: BUG: unable to handle kernel paging request at 00007ffd1d6b43a0 IP: [<ffffffffaa7a882a>] string.isra.7+0x6a/0xf0 Oops: 0003 [#1] SMP Call Trace: [<ffffffffaa7a9f31>] vsnprintf+0x201/0x6a0 [<ffffffffaa7aa556>] sprintf+0x56/0x80 [<ffffffffc04227ed>] qedf_dbg_stop_io_on_error_cmd_read+0x6d/0x90 [qedf] [<ffffffffaa65bb2f>] vfs_read+0x9f/0x170 [<ffffffffaa65cb82>] SyS_pread64+0x92/0xc0 Avoid this by preparing the info in a kernel buffer first, either allocated on stack for small printouts, or via vmalloc() for big ones, and then copying it to the userspace properly. Previous submission is an RFC: [1]. There are no code changes since then. The RFC prefix is dropped. The Tested-by tag from Laurence is added. There's similar submission from Saurav [2], but we agreed I could nack it and proceed with my one. [1] https://lore.kernel.org/linux-scsi/20230724120241.40495-1-oleksandr@redhat.com/ [2] https://lore.kernel.org/linux-scsi/20230726101236.11922-1-skashyap@marvell.com/ Oleksandr Natalenko (3): scsi: qedf: do not touch __user pointer in qedf_dbg_stop_io_on_error_cmd_read() directly scsi: qedf: do not touch __user pointer in qedf_dbg_debug_cmd_read() directly scsi: qedf: do not touch __user pointer in qedf_dbg_fp_int_cmd_read() directly drivers/scsi/qedf/qedf_dbg.h | 2 ++ drivers/scsi/qedf/qedf_debugfs.c | 35 +++++++++++++++++++------------- 2 files changed, 23 insertions(+), 14 deletions(-)