* [PATCH AUTOSEL 4.14 30/37] floppy: fix div-by-zero in setup_format_params
[not found] <20190726134332.12626-1-sashal@kernel.org>
@ 2019-07-26 13:43 ` Sasha Levin
2019-07-26 13:43 ` [PATCH AUTOSEL 4.14 31/37] floppy: fix out-of-bounds read in copy_buffer Sasha Levin
1 sibling, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2019-07-26 13:43 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Denis Efremov, Willy Tarreau, Linus Torvalds, Sasha Levin, linux-block
From: Denis Efremov <efremov@ispras.ru>
[ Upstream commit f3554aeb991214cbfafd17d55e2bfddb50282e32 ]
This fixes a divide by zero error in the setup_format_params function of
the floppy driver.
Two consecutive ioctls can trigger the bug: The first one should set the
drive geometry with such .sect and .rate values for the F_SECT_PER_TRACK
to become zero. Next, the floppy format operation should be called.
A floppy disk is not required to be inserted. An unprivileged user
could trigger the bug if the device is accessible.
The patch checks F_SECT_PER_TRACK for a non-zero value in the
set_geometry function. The proper check should involve a reasonable
upper limit for the .sect and .rate fields, but it could change the
UAPI.
The patch also checks F_SECT_PER_TRACK in the setup_format_params, and
cancels the formatting operation in case of zero.
The bug was found by syzkaller.
Signed-off-by: Denis Efremov <efremov@ispras.ru>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/floppy.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 3ea9c3e9acb3..4c6c20376a83 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -2114,6 +2114,9 @@ static void setup_format_params(int track)
raw_cmd->kernel_data = floppy_track_buffer;
raw_cmd->length = 4 * F_SECT_PER_TRACK;
+ if (!F_SECT_PER_TRACK)
+ return;
+
/* allow for about 30ms for data transport per track */
head_shift = (F_SECT_PER_TRACK + 5) / 6;
@@ -3238,6 +3241,8 @@ static int set_geometry(unsigned int cmd, struct floppy_struct *g,
/* sanity checking for parameters. */
if (g->sect <= 0 ||
g->head <= 0 ||
+ /* check for zero in F_SECT_PER_TRACK */
+ (unsigned char)((g->sect << 2) >> FD_SIZECODE(g)) == 0 ||
g->track <= 0 || g->track > UDP->tracks >> STRETCH(g) ||
/* check if reserved bits are set */
(g->stretch & ~(FD_STRETCH | FD_SWAPSIDES | FD_SECTBASEMASK)) != 0)
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH AUTOSEL 4.14 31/37] floppy: fix out-of-bounds read in copy_buffer
[not found] <20190726134332.12626-1-sashal@kernel.org>
2019-07-26 13:43 ` [PATCH AUTOSEL 4.14 30/37] floppy: fix div-by-zero in setup_format_params Sasha Levin
@ 2019-07-26 13:43 ` Sasha Levin
1 sibling, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2019-07-26 13:43 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Denis Efremov, Willy Tarreau, Linus Torvalds, Sasha Levin, linux-block
From: Denis Efremov <efremov@ispras.ru>
[ Upstream commit da99466ac243f15fbba65bd261bfc75ffa1532b6 ]
This fixes a global out-of-bounds read access in the copy_buffer
function of the floppy driver.
The FDDEFPRM ioctl allows one to set the geometry of a disk. The sect
and head fields (unsigned int) of the floppy_drive structure are used to
compute the max_sector (int) in the make_raw_rw_request function. It is
possible to overflow the max_sector. Next, max_sector is passed to the
copy_buffer function and used in one of the memcpy calls.
An unprivileged user could trigger the bug if the device is accessible,
but requires a floppy disk to be inserted.
The patch adds the check for the .sect * .head multiplication for not
overflowing in the set_geometry function.
The bug was found by syzkaller.
Signed-off-by: Denis Efremov <efremov@ispras.ru>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/floppy.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 4c6c20376a83..1205472a9f63 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3239,8 +3239,10 @@ static int set_geometry(unsigned int cmd, struct floppy_struct *g,
int cnt;
/* sanity checking for parameters. */
- if (g->sect <= 0 ||
- g->head <= 0 ||
+ if ((int)g->sect <= 0 ||
+ (int)g->head <= 0 ||
+ /* check for overflow in max_sector */
+ (int)(g->sect * g->head) <= 0 ||
/* check for zero in F_SECT_PER_TRACK */
(unsigned char)((g->sect << 2) >> FD_SIZECODE(g)) == 0 ||
g->track <= 0 || g->track > UDP->tracks >> STRETCH(g) ||
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
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2019-07-26 13:43 ` [PATCH AUTOSEL 4.14 30/37] floppy: fix div-by-zero in setup_format_params Sasha Levin
2019-07-26 13:43 ` [PATCH AUTOSEL 4.14 31/37] floppy: fix out-of-bounds read in copy_buffer Sasha Levin
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