On 04/08/2022 3:32 pm, Dan Carpenter wrote:
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")
FWIW I think this has actually been broken since day one back in
14e0e6796a0d, but I'm also not inclined to care that much - 2014 is
already plenty long ago.
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
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)); \
I suppose snprintf is OK in practice since none of the names are
anywhere near 20 characters long anyway, but I agree it's better to be
obviously foolproof. Frankly this code is all kinds of horrible anyway,
and deserves ripping out and replacing with a simple seq_file, but for
this fix as a fix,
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Cheers,
Robin.
p += bytes; \
len -= bytes; \
- if (len < maxcol) \
- goto out; \
} while (0)
static ssize_t
