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| author |   Denis Efremov <efremov@ispras.ru> | 2019-07-12 21:55:23 +0300 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-17 14:45:50 -0700 |
| commit | da99466ac243f15fbba65bd261bfc75ffa1532b6 (patch) | |
| tree | a4078e6242803b3e1e5dd294fa0ad5fa52f4f9a3 /drivers/block/floppy.c | |
| parent | floppy: fix invalid pointer dereference in drive_name (diff) | |
| download | linux-dev-da99466ac243f15fbba65bd261bfc75ffa1532b6.tar.xz linux-dev-da99466ac243f15fbba65bd261bfc75ffa1532b6.zip | |
floppy: fix out-of-bounds read in copy_buffer
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>
Diffstat (limited to '')
| -rw-r--r-- | drivers/block/floppy.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index 671a0ae434b4..fee57f7f3821 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -3233,8 +3233,10 @@ 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) || |