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CVE-2019-13106: ext4: fix out-of-bounds memset

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In ext4fs_read_file in ext4fs.c, a memset can overwrite the bounds of
the destination memory region. This patch adds a check to disallow
this.

Signed-off-by: Paul Emge <paulemge@forallsecure.com>
This commit is contained in:
Paul Emge 2019-07-08 16:37:07 -07:00 committed by Tom Rini
parent 084be43b75
commit e205896c53
1 changed files with 5 additions and 2 deletions
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7
fs/ext4/ext4fs.c
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@ -61,6 +61,7 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
lbaint_t delayed_skipfirst = 0;
lbaint_t delayed_next = 0;
char *delayed_buf = NULL;
char *start_buf = buf;
short status;
struct ext_block_cache cache;
@ -139,6 +140,7 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
}
} else {
int n;
int n_left;
if (previous_block_number != -1) {
/* spill */
status = ext4fs_devread(delayed_start,
@ -153,8 +155,9 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
}
/* Zero no more than `len' bytes. */
n = blocksize - skipfirst;
if (n > len)
n = len;
n_left = len - ( buf - start_buf );
if (n > n_left)
n = n_left;
memset(buf, 0, n);
}
buf += blocksize - skipfirst;