(Potentially undefined behavior): strncmp with N greater than zero for an array of size zero.

[safocl]

ntfs-3g/ntfsprogs/ntfsinfo.c

Line 2150 in 75dcdc2

!strncmp((const char*)"SETFILEBITS",

strncmp((const char*)"SETFILEBITS",
				(const char*)ea->name, 11)

but

ntfs-3g/include/ntfs-3g/layout.h

Line 2514 in 75dcdc2

u8 name[0]; /* Name of the EA. */

typedef struct {
	le32 next_entry_offset;	/* Offset to the next EA_ATTR. */
	EA_FLAGS flags;		/* Flags describing the EA. */
	u8 name_length;		/* Length of the name of the extended
				   attribute in bytes. */
	le16 value_length;	/* Byte size of the EA's value. */
	u8 name[0];		/* Name of the EA. */
	u8 value[0];		/* The value of the EA. Immediately
				   follows the name. */
} __attribute__((__packed__)) EA_ATTR;

and

The behavior is undefined when access occurs past the end of either array lhs or rhs. The behavior is undefined when either lhs or rhs is the null pointer.

[safocl]

is this expression ever true?

ntfs-3g/ntfsprogs/ntfsinfo.c

Line 2149 in 75dcdc2

if (ea->name_length == 11 &&

ea->name_length == 11

[safocl]

https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html

Declaring zero-length arrays in other contexts, including as interior members of structure objects or as non-member objects, is discouraged. Accessing elements of zero-length arrays declared in such contexts is undefined and may be diagnosed.

A structure containing a C99 flexible array member, or a union containing such a structure, is not the last field of another structure, for example:

struct flex { int length; char data[]; };

struct mid_flex { int m; struct flex flex_data; int n; };

In the above, accessing a member of the array mid_flex.flex_data.data[] might have undefined behavior. Compilers do not handle such a case consistently. Any code relying on this case should be modified to ensure that flexible array members only end up at the ends of structures.

Please use the warning option -Wflex-array-member-not-at-end to identify all such cases in the source code and modify them. This extension is now deprecated.