Le 05/09/2023 à 07:04, Damien Le Moal a écrit :
On 9/5/23 04:54, Christophe JAILLET wrote:
snprintf() returns the "number of characters which *would* be generated for
the given input", not the size *really* generated.
In order to avoid too large values for 'o' (and potential negative values
for "sizeof(linebuf) o") use scnprintf() instead of snprintf().
Note that given the "w < 4" in the for loop, the buffer can NOT
overflow, but using the *right* function is always better.
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Doesn't this need Fixes and CC stable tags ?
I don't think so.
As said in the commit message :
Note that given the "w < 4" in the for loop, the buffer can NOT
overflow, but using the *right* function is always better.
linebuf is 38 chars.
In each iteration, we write 9 bytes + NULL.
We write only 4 elements per line (because of w < 4), so 9 * 4 + 1 = 37
bytes are needed.
9 is for %08x<space>
It can't overflow.
Moreover, it is really unlikely that the size of linebuf or the number
of elements on each line change in a stable kernel.
So, from my POV, this patch is more a clean-up than anything else.
I would even agree that it is maybe not even needed. But should someone
cut'n'paste it one day, then using the correct function could maybe help
him.
CJ
---
drivers/ata/sata_mv.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index d105db5c7d81..45e48d653c60 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -1255,8 +1255,8 @@ static void mv_dump_mem(struct device *dev, void __iomem *start, unsigned bytes)
for (b = 0; b < bytes; ) {
for (w = 0, o = 0; b < bytes && w < 4; w++) {
- o += snprintf(linebuf + o, sizeof(linebuf) - o,
- "%08x ", readl(start + b));
+ o += scnprintf(linebuf + o, sizeof(linebuf) - o,
+ "%08x ", readl(start + b));
b += sizeof(u32);
}
dev_dbg(dev, "%s: %p: %s\n",
