[PATCH 5.19 516/717] iommu/omap: Fix buffer overflow in debugfs

Greg Kroah-Hartman
2022-10-22T08:22:31Z

From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 184233a5202786b20220acd2d04ddf909ef18f29 ]

There are two issues here:

1) The "len" variable needs to be checked before the very first write.
Otherwise if omap2_iommu_dump_ctx() with "bytes" less than 32 it is a
buffer overflow.
2) The snprintf() function returns the number of bytes that *would* have
been copied if there were enough space. But we want to know the
number of bytes which were *actually* copied so use scnprintf()
instead.

Fixes: bd4396f09a4a ("iommu/omap: Consolidate OMAP IOMMU modules")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/YuvYh1JbE3v+abd5@kili
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/omap-iommu-debug.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/omap-iommu-debug.c b/drivers/iommu/omap-iommu-debug.c
index a99afb5d9011..259f65291d90 100644
--- a/drivers/iommu/omap-iommu-debug.c
+++ b/drivers/iommu/omap-iommu-debug.c
@@ -32,12 +32,12 @@ static inline bool is_omap_iommu_detached(struct omap_iommu *obj)
ssize_t bytes; \
const char *str = "%20s: %08x\n"; \
const int maxcol = 32; \
- bytes = snprintf(p, maxcol, str, __stringify(name), \
+ if (len < maxcol) \
+ goto out; \
+ bytes = scnprintf(p, maxcol, str, __stringify(name), \
iommu_read_reg(obj, MMU_##name)); \
p += bytes; \
len -= bytes; \
- if (len < maxcol) \
- goto out; \
} while (0)

static ssize_t
--
2.35.1