[PATCH 1/5] altera-stapl: altera_get_note: prevent write beyond end of 'key'

Daniel Axtens
2020-01-20T07:44:16Z

altera_get_note is called from altera_init, where key is kzalloc(33).

When the allocation functions are annotated to allow the compiler to see
the sizes of objects, and with FORTIFY_SOURCE, we see:

In file included from drivers/misc/altera-stapl/altera.c:14:0:
In function ‘strlcpy’,
inlined from ‘altera_init’ at drivers/misc/altera-stapl/altera.c:2189:5:
include/linux/string.h:378:4: error: call to ‘__write_overflow’ declared with attribute error: detected write beyond size of object passed as 1st parameter
__write_overflow();
^~~~~~~~~~~~~~~~~~

That refers to this code in altera_get_note:

if (key != NULL)
strlcpy(key, &p[note_strings +
get_unaligned_be32(
&p[note_table + (8 * i)])],
length);

The error triggers because the length of 'key' is 33, but the copy
uses length supplied as the 'length' parameter, which is always
256. Split the size parameter into key_len and val_len, and use the
appropriate length depending on what is being copied.

Detected by compiler error, only compile-tested.

Cc: "Igor M. Liplianin" <liplianin@netup.ru>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
drivers/misc/altera-stapl/altera.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/altera-stapl/altera.c b/drivers/misc/altera-stapl/altera.c
index 25e5f24b3fec..5bdf57472314 100644
--- a/drivers/misc/altera-stapl/altera.c
+++ b/drivers/misc/altera-stapl/altera.c
@@ -2112,8 +2112,8 @@ static int altera_execute(struct altera_state *astate,
return status;
}

-static int altera_get_note(u8 *p, s32 program_size,
- s32 *offset, char *key, char *value, int length)
+static int altera_get_note(u8 *p, s32 program_size, s32 *offset,
+ char *key, char *value, int keylen, int vallen)
/*
* Gets key and value of NOTE fields in the JBC file.
* Can be called in two modes: if offset pointer is NULL,
@@ -2170,7 +2170,7 @@ static int altera_get_note(u8 *p, s32 program_size,
&p[note_table + (8 * i) + 4])];

if (value != NULL)
- strlcpy(value, value_ptr, length);
+ strlcpy(value, value_ptr, vallen);

}
}
@@ -2189,13 +2189,13 @@ static int altera_get_note(u8 *p, s32 program_size,
strlcpy(key, &p[note_strings +
get_unaligned_be32(
&p[note_table + (8 * i)])],
- length);
+ keylen);

if (value != NULL)
strlcpy(value, &p[note_strings +
get_unaligned_be32(
&p[note_table + (8 * i) + 4])],
- length);
+ vallen);

*offset = i + 1;
}
@@ -2449,7 +2449,7 @@ int altera_init(struct altera_config *config, const struct firmware *fw)
__func__, (format_version == 2) ? "Jam STAPL" :
"pre-standardized Jam 1.1");
while (altera_get_note((u8 *)fw->data, fw->size,
- &offset, key, value, 256) == 0)
+ &offset, key, value, 32, 256) == 0)
printk(KERN_INFO "%s: NOTE \"%s\" = \"%s\"\n",
__func__, key, value);
}
--
2.20.1